Code Knowledgebase

A short history of Git

Sun, 01 Nov 2026 00:00:00 GMT

Git began in 2005 when the Linux kernel lost BitKeeper and needed a new distributed version control system fast. This overview follows Linus Torvalds' design goals, Junio Hamano's long stewardship, GitHub's rise, and the defaults and hash algorithms teams use today.

A short history of JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

JavaScript began as a ten-day prototype in a browser and became the shared runtime of the web, servers, and tools. This overview follows that arc from Netscape in 1995 through ECMAScript, Node.js, transpilers, and today's yearly language releases.

A short history of MongoDB

Sun, 01 Nov 2026 00:00:00 GMT

Document databases grew out of web-scale workloads that relational schemas struggled to keep up with. This overview situates MongoDB in the NoSQL landscape and follows the product from 10gen through WiredTiger, Atlas, transactions, and today's search and embedding features.

A short history of Unix and Linux

Sun, 01 Nov 2026 00:00:00 GMT

Unix began as a research operating system at Bell Labs and grew into a family of standards and kernels. This overview traces BSD and GNU, the 1991 Linux kernel, the GPL, how distributions bundle the stack, and where Linux runs today—from servers to Android.

Accepting payments with Stripe Checkout

Sun, 01 Nov 2026 00:00:00 GMT

Stripe Checkout hosts the payment UI on Stripe's domain: your server creates a Session, the browser redirects, and webhooks confirm the sale. This runbook wires Checkout into Express for one-time Prices with success and cancel pages.

Advanced Git

Sun, 01 Nov 2026 00:00:00 GMT

Revision syntax, log search, blame, reflog, history filtering, bisect, worktrees, hooks, and rerere—for when everyday commands are not enough to find a commit, recover a lost branch, or automate repository policy.

Application lifecycle hooks in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

NestJS calls methods on your providers at fixed points while the application starts and stops. This chapter lists the hooks and their order, shows where startup work and cleanup belong, and explains why shutdown hooks have to be switched on before a container stop is handled gracefully.

Artifact Registry

Sun, 01 Nov 2026 00:00:00 GMT

Artifact Registry stores build artifacts such as Docker images and npm packages in regional repositories with IAM and optional scanning. This chapter creates a Docker repository, authenticates docker push, and publishes the series file API image.

Astro cheat sheet

Sun, 01 Nov 2026 00:00:00 GMT

CLI commands, special files, component syntax, directives, routing patterns, and content collection functions in one scannable page, meant to sit beside the Astro series.

Astro components

Sun, 01 Nov 2026 00:00:00 GMT

An .astro file is a server-side script and an HTML template in one file. This page covers the component script, template expressions, typed props, slots, scoped styles, client scripts, and the Image component, which together make up most of the Astro code you will write.

Async/await in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

Async functions always return a Promise, and await pauses until a Promise settles—giving sequential async code without nested then chains. This chapter covers syntax, parallel awaits, and error handling patterns.

Async iterators and for await..of

Sun, 01 Nov 2026 00:00:00 GMT

Async iterables produce values that may arrive after await, which fits streams, paginated APIs, and backpressure-friendly pipelines. This chapter covers Symbol.asyncIterator, async generators, and for await..of consumption.

Authentication and authorization in GraphQL

Sun, 01 Nov 2026 00:00:00 GMT

GraphQL needs identity in context and authorization at field granularity. This chapter covers transport auth, resolver and field guards, NestJS GqlExecutionContext, node(id) IDOR risks, and subscription connection_init.

Authentication in MongoDB

Sun, 01 Nov 2026 00:00:00 GMT

MongoDB separates who you are from what you may do. Authentication verifies identity with SCRAM; authorization assigns roles on databases and collections. This page covers users, built-in roles, connection strings, Docker bootstrap credentials, and Atlas database users from application code.

Authentication in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

NestJS authentication is built from guards: one checks a password and issues a token, another verifies that token on every later request. This chapter wires Passport's local and JWT strategies into a Nest app, then protects every route by default with a global guard and a @Public() opt-out.

Authorization in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

Once a NestJS request has a user, authorization decides what that user may do. This chapter builds role checks from a typed decorator and a guard, orders them after authentication, adds a @CurrentUser() parameter, and moves ownership checks into the service where the data is.

Booting Linux and systemd

Sun, 01 Nov 2026 00:00:00 GMT

From firmware to login, boot is a chain of loaders, an initial RAM disk, and PID 1. This overview covers UEFI and GRUB, initramfs, systemd units and targets, journald, and how Debian differs from older init and macOS launchd at a glance.

Breaking up long tasks

Sun, 01 Nov 2026 00:00:00 GMT

A page that ignores clicks for a moment, a spinner that never appears, or a poor Interaction to Next Paint score usually has one cause: a single task holding the main thread. This page shows how to confirm it, why await alone does not help, and the three fixes — yield, defer, or move the work.

Building a GraphQL server with NestJS

Sun, 01 Nov 2026 00:00:00 GMT

NestJS can expose a code-first GraphQL API with the Apollo driver, auto- generated SDL, decorators for types and resolvers, validation pipes, request- scoped DataLoaders, and graphql-ws subscriptions. This runbook walks from install to a working endpoint.

Callbacks and timers

Sun, 01 Nov 2026 00:00:00 GMT

Host APIs still expose completion handlers as functions you pass in. This chapter covers callback conventions, setTimeout and setInterval, and why nested callbacks led to promises and async/await.

Cancellation with AbortController

Sun, 01 Nov 2026 00:00:00 GMT

Promises do not cancel themselves; AbortController provides a standard signal for fetch, streams, and your own async tasks. This chapter covers signals, abort reasons, and cleaning up listeners when work is no longer needed.

Classes in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

class syntax is mostly syntactic sugar over prototypes: constructors install own state, methods live on the prototype, extends wires the chain. Fields, private #members, and static blocks match what Java or C# developers expect with a few JavaScript-specific rules.

Cloud Logging

Sun, 01 Nov 2026 00:00:00 GMT

Cloud Logging ingests logs from Cloud Run, load balancers, and your app’s stdout. This chapter writes structured JSON from the series API, queries logs in Logs Explorer, and outlines sinks and audit logs.

Cloud Monitoring

Sun, 01 Nov 2026 00:00:00 GMT

Cloud Monitoring collects metrics from Cloud Run and load balancers, builds dashboards, and fires alerts. This chapter explores key metrics, uptime checks, alerting policies, and SLOs for the series file API.

Code review and pull request hygiene

Sun, 01 Nov 2026 00:00:00 GMT

Good pull requests are small, test-backed, and easy to revert; good reviews focus on design and risk, not style nitpicks. Practices for authors and reviewers when Git history is shared on a protected main branch.

Collaborating with Git

Sun, 01 Nov 2026 00:00:00 GMT

Git stores history; teams add agreements on top—who merges, how branches are named, and how review happens before code reaches main. This overview maps those social layers to remotes, pull requests, and protected branches.

Concurrency with workers

Sun, 01 Nov 2026 00:00:00 GMT

Workers are how JavaScript runs in parallel: each one is a separate thread with its own heap and event loop, talking to the others through messages. This chapter covers starting workers in browsers and Node, what copying, transferring, and sharing memory each cost, and which kind of worker fits which job.

Configuration in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

@nestjs/config loads environment variables and .env files into an injectable ConfigService. This chapter covers loading and precedence, namespaced and typed configuration, failing fast on missing values, and giving each feature module only the settings it needs.

Content collections in Astro

Sun, 01 Nov 2026 00:00:00 GMT

Content collections give Markdown, JSON, and remote data a schema, typed queries, and validation at build time. This page defines collections with the glob and file loaders, validates frontmatter with Zod, links entries with references, and generates one page per entry.

Continuous delivery with Cloud Build

Sun, 01 Nov 2026 00:00:00 GMT

Cloud Build runs containerized build steps on Google’s infrastructure and can push to Artifact Registry and deploy Cloud Run. This chapter defines cloudbuild.yaml for the series API and outlines GitHub triggers.

Control flow in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

if and switch follow C-shaped syntax, but switch uses strict equality and falls through unless you break. Labeled break and continue apply to any statement, not only loops—a feature most statically typed languages omit. Ternary expressions fill the same niche as other languages’ inline conditionals.

Controllers in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

Controllers map HTTP routes to methods and turn their return values into responses. This chapter covers route decorators, reading parameters, query strings and bodies into DTOs, status codes and headers, and the escape hatch to the underlying Express response.

Creating an Astro project

Sun, 01 Nov 2026 00:00:00 GMT

Scaffold a project with the create-astro wizard, learn which folders Astro treats specially, and run the dev, build, preview, and check commands. The steps end with a configured project ready for the rest of the series.

CRUD operations in MongoDB

Sun, 01 Nov 2026 00:00:00 GMT

Documents are BSON records in collections; the Node.js driver maps them to TypeScript types. This chapter walks through insert, find, update, and delete with filters, projections, array operators, upserts, bulk writes, and the ObjectId versus string boundary at HTTP APIs.

Custom payment forms with the Payment Element

Sun, 01 Nov 2026 00:00:00 GMT

When Checkout's hosted page is not enough, embed the Payment Element: your server creates a PaymentIntent, the browser mounts Stripe.js UI, and confirmPayment finishes authentication. This runbook compares that path with Checkout for Express apps.

Customers in Stripe

Sun, 01 Nov 2026 00:00:00 GMT

A Stripe Customer is the billing profile for someone in your app: email, metadata, and saved payment methods. This chapter shows how to create customers at signup, map them to your user ids, and save cards for on-session and off-session charges with SetupIntents.

Data types in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

ECMAScript divides values into seven primitives and Object. typeof is the everyday type check, but it has well-known holes. This overview maps the type system and points to chapters on copying, coercion, numbers, strings, and symbols.

Dates and Temporal

Sun, 01 Nov 2026 00:00:00 GMT

Date has been the built-in clock since ES1, but mutability and time-zone gaps push new code toward Temporal. This comparison covers what Date still does, what Temporal fixes, and how to choose in browsers and Node today.

Deploying containers with Cloud Run

Sun, 01 Nov 2026 00:00:00 GMT

Cloud Run runs stateless containers on demand with HTTPS URLs, revisions, and autoscaling. This chapter deploys the series file API from Artifact Registry, configures the runtime service account, scaling, and ingress.

Destructuring and spread

Sun, 01 Nov 2026 00:00:00 GMT

Destructuring unpacks arrays and objects into bindings; spread copies iterables and expands objects in literals. Together they replace much of the manual indexing common in Java or Go. Rest in patterns collects leftovers without the arguments object.

Dynamic modules in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

forRoot(), forFeature(), and forRootAsync() are how NestJS modules accept options from the application that imports them. This chapter shows what a dynamic module returns, the naming conventions, async configuration through the injector, and generating the boilerplate with ConfigurableModuleBuilder.

ECMAScript versions cheat sheet

Sun, 01 Nov 2026 00:00:00 GMT

Each yearly ECMAScript edition bundles finished proposals. This cheat sheet lists headline additions from ES5 through recent editions so you can map syntax you see in tutorials to the standard that introduced it.

Everyday Git commands

Sun, 01 Nov 2026 00:00:00 GMT

Configure identity, create commits, inspect history, manage branches, and ignore build artifacts—the commands you use on most working days. Assumes you know how Git's working tree, index, and repository fit together.

Evolving a GraphQL schema

Sun, 01 Nov 2026 00:00:00 GMT

GraphQL favors continuous schema evolution over versioned URLs. This chapter classifies safe and breaking changes, documents @deprecated fields and enum values, outlines a deprecation workflow, and shows deprecationReason in NestJS code-first schemas.

Exception filters in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

Exception filters are where a NestJS application decides what an error looks like to the client. This chapter covers the built-in HTTP exceptions, attaching a cause, custom exception classes, writing a filter, and a catch-all filter that gives every error one shape.

Execution contexts and the call stack

Sun, 01 Nov 2026 00:00:00 GMT

Every running piece of code has an execution context that says where its variables are, what this is, and which realm's built-ins it sees. This chapter follows contexts onto and off the call stack, explains hoisting, closures, suspension, and realms in those terms, and shows how to read the stack traces that come out of it.

Finding memory leaks

Sun, 01 Nov 2026 00:00:00 GMT

A JavaScript leak is memory the program can still reach but will never use again. This page is the procedure for finding one: confirm the growth survives garbage collection, use heap snapshots to find what is retained and by what, then fix the reference. It ends with the causes behind most leaks.

Formatting and validating Terraform files

Sun, 01 Nov 2026 00:00:00 GMT

Consistent HCL and early validation catch mistakes before plan or apply. This page covers terraform fmt and validate, variable and lifecycle checks, TFLint, pre-commit hooks, and a minimal CI gate—with a pointer to terraform test for module regressions.

QuickTip: Freezing and sealing objects

Sun, 01 Nov 2026 00:00:00 GMT

Object.preventExtensions, seal, and freeze tighten what can change on an object—useful for config snapshots and defensive copies, not deep immutability.

From source code to machine code

Sun, 01 Nov 2026 00:00:00 GMT

An engine has to start running code within milliseconds and still end up with fast machine code for the functions that matter. This chapter follows a function through V8's parser, interpreter, and three compilers, shows how type feedback drives optimization, and explains why optimized code gets thrown away.

Full-text search in MongoDB

Sun, 01 Nov 2026 00:00:00 GMT

Community deployments offer regex and text indexes; Atlas Search adds Lucene- style analyzers, fuzzy matching, and facets. This chapter compares those paths, defines Atlas Search indexes from TypeScript, runs $search locally on Atlas Local, and paginates with searchAfter.

Functional patterns in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

IIFEs isolate scope before modules were universal; currying, compose, and memoize express reusable function plumbing. JavaScript is multi-paradigm—these patterns are idiomatic where they reduce noise, not mandatory style.

Functions in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

Functions are first-class values: declarations hoist differently from const bindings, arrow functions inherit lexical this, and the rest parameter replaces most uses of the arguments object. Default parameters run at call time and can reference earlier parameters—unlike overload sets in Java or C#.

Geospatial queries in MongoDB

Sun, 01 Nov 2026 00:00:00 GMT

Location-aware apps store coordinates as GeoJSON and query them with 2dsphere indexes. This chapter covers point and polygon shapes, near and within operators, geoNear in aggregation, legacy 2d indexes, and a store locator example in TypeScript.

Getting started with Terraform on Google Cloud

Sun, 01 Nov 2026 00:00:00 GMT

A step-by-step runbook to install Terraform, authenticate with Google Cloud, and manage a storage bucket, a VPC, and a small Compute Engine VM through init, plan, apply, and destroy—using the standard file layout.

Getting started with urql

Sun, 01 Nov 2026 00:00:00 GMT

urql 5 wires React apps to GraphQL through a client, exchanges, and hooks. This chapter shows createClient with cacheExchange and fetchExchange, auth headers, request policies, mutations, document-cache invalidation, and subscription exchanges.

Git cheat sheet

Sun, 01 Nov 2026 00:00:00 GMT

Scannable Git commands for daily work—config, commits, branches, remotes, undo, and merge—grouped for quick lookup beside the Git and GitHub series.

Git glossary

Sun, 01 Nov 2026 00:00:00 GMT

Git and GitHub terms used across the series—blob, index, rebase, pull request, and more—each defined briefly and linked to the chapter that explains the idea in depth.

Git workflows for teams

Sun, 01 Nov 2026 00:00:00 GMT

Trunk-based development, Git Flow, and GitHub Flow compared—how branch lifetimes, release cadence, and CI maturity drive the model, plus scaling patterns for monorepos and open source.

GitHub Actions

Sun, 01 Nov 2026 00:00:00 GMT

GitHub Actions runs workflows on Git events—push, pull request, schedule— using YAML in .github/workflows. This overview covers jobs, steps, runners, reusable actions, secrets, matrices, caching, and a complete Node CI pipeline you can adapt.

Google Cloud glossary

Sun, 01 Nov 2026 00:00:00 GMT

Google Cloud Platform terms used in the series—project, service account, Artifact Registry, Cloud Run revision, and more—each defined briefly and linked to the chapter that goes deeper.

Graphical desktops on Linux

Sun, 01 Nov 2026 00:00:00 GMT

Linux graphics stack from kernel modesetting through compositors and toolkits to desktop environments. This overview compares X11 and Wayland, GNOME and KDE on Debian, display managers, and GTK versus Qt.

GraphQL clients compared

Sun, 01 Nov 2026 00:00:00 GMT

Browsers and React apps can talk to GraphQL with fetch, thin wrappers, urql, Apollo Client, Relay, or TanStack Query. This comparison covers what each layer adds—caching, codegen, normalized stores—and when to pick one.

GraphQL federation

Sun, 01 Nov 2026 00:00:00 GMT

Federation lets independent teams publish subgraphs that compose into one supergraph queried through a router. This overview explains composition, entities and @key, migration directives, major platforms, a NestJS subgraph sketch, and when federation is worth the operational cost.

GraphQL glossary

Sun, 01 Nov 2026 00:00:00 GMT

Terms used across the GraphQL series—from schema and SDL through resolvers, urql exchanges, deprecation, persisted queries, and federation—each defined briefly and linked to the chapter that goes deeper.

Guards in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

A guard answers one question before a NestJS handler runs: may this request continue? This chapter covers the CanActivate contract, reading the request and the handler from the ExecutionContext, steering a guard with metadata, and binding guards to routes or to the whole application.

Hardware and devices in Linux

Sun, 01 Nov 2026 00:00:00 GMT

Drivers, firmware, and device nodes connect the kernel to hardware. This overview explains /dev, udev, block devices and partitions, firmware on Debian, and how USB and PCI devices appear on a running system.

HCL structure in Terraform

Sun, 01 Nov 2026 00:00:00 GMT

HashiCorp Configuration Language is how Terraform files declare providers, resources, variables, and outputs. This page walks through blocks and expressions, meta-arguments, dependency graphs, and sensible file layout—with Google Cloud examples throughout.

Hidden classes and inline caches

Sun, 01 Nov 2026 00:00:00 GMT

In the language, an object is a bag of named properties that can change at any time. Engines make property access fast anyway by giving objects hidden shapes and caching what each access site has seen. This chapter shows how shapes form, what breaks them, how arrays get the same treatment, and how to check it yourself.

Higher-order functions and callbacks

Sun, 01 Nov 2026 00:00:00 GMT

Functions are first-class values: pass them as arguments, return them, store them in data structures. Array methods and async APIs build on that model— familiar if you have used map/filter in Python or streams in Java.

How ECMAScript is standardized

Sun, 01 Nov 2026 00:00:00 GMT

ECMAScript is maintained by TC39 at Ecma International. Proposals move through numbered stages, are validated by test262, and ship as yearly editions — separate from HTML, fetch, and other host specifications.

How Git works

Sun, 01 Nov 2026 00:00:00 GMT

Git tracks snapshots of your project as commits linked in a graph, not as a single linear tape of diffs. This page explains what version control is solving, the four areas where your files live during a command, and how blobs, trees, and commits fit together.

IAM in Google Cloud

Sun, 01 Nov 2026 00:00:00 GMT

Cloud IAM decides who can call which API on which resource. This chapter covers principals, roles, allow policies, service accounts, and least privilege, then creates deployer and runtime identities for the series file API.

Indexes and query performance in MongoDB

Sun, 01 Nov 2026 00:00:00 GMT

Indexes turn collection scans into range or point lookups. This chapter covers single and compound indexes, the ESR rule, specialty indexes, explain plans, covered queries, creating indexes from TypeScript, and capped and time series collections.

Input types and arguments

Sun, 01 Nov 2026 00:00:00 GMT

Arguments tune individual fields; input object types bundle structured write payloads. GraphQL keeps input and output types separate, which shapes how you design mutations, validate data, and avoid breaking clients when forms evolve.

Installing and connecting to MongoDB

Sun, 01 Nov 2026 00:00:00 GMT

You can run MongoDB locally in Docker, exercise Atlas Search features with the Atlas Local image, or use a free Atlas cluster in the cloud. This runbook installs those options and connects from TypeScript with the official Node.js driver, pooling, and a clean shutdown path.

Interceptors in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

An interceptor wraps a NestJS route handler, so it can act both before the handler runs and on whatever the handler returns. This chapter covers the NestInterceptor contract, the RxJS operators that do most of the work, and the built-in interceptors for serialization and caching.

Internationalization with Intl

Sun, 01 Nov 2026 00:00:00 GMT

Intl formats numbers, dates, lists, and plural messages using locale data built into the engine—without shipping your own locale files for common cases. This page maps the main constructors and when to reach for each.

Islands and client directives in Astro

Sun, 01 Nov 2026 00:00:00 GMT

Client directives decide whether a framework component stays static HTML or hydrates in the browser, and when. This page covers framework integrations, the five client directives, what props can cross into an island, sharing state between islands, server islands, and client-side navigation with view transitions.

Iterator helpers

Sun, 01 Nov 2026 00:00:00 GMT

ES2025 adds lazy iterator objects with map, filter, take, and related helpers so you can chain sequence operations without copying arrays. This chapter covers Iterator.from, chaining, and when helpers beat array methods.

JavaScript engine glossary

Sun, 01 Nov 2026 00:00:00 GMT

The Under the Hood series uses terms from three sources: the ECMAScript specification, the HTML Standard's event loop, and the engines' own documentation. This glossary defines each of them in a sentence or two, grouped by topic, and links to the chapter that explains it.

JavaScript syntax at a glance

Sun, 01 Nov 2026 00:00:00 GMT

JavaScript blurs the line between statements and expressions more than C-style languages do, and parsers apply automatic semicolon insertion when you omit terminators. This chapter maps strict mode, script versus module goals, and the syntactic habits that surprise newcomers from Java, Go, or Python.

JSON in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

JSON.parse and JSON.stringify are the built-in bridge between JavaScript values and UTF-8 text. This page covers syntax limits, revivers/replacers, and safe parsing—plus where jq fits when JSON lives in shell pipelines.

Limiting query depth and cost

Sun, 01 Nov 2026 00:00:00 GMT

Depth limits, complexity analysis, alias caps, timeouts, persisted query allowlists, and disabling introspection protect GraphQL from expensive operations. This chapter shows NestJS complexity plugins and gateway-level controls.

Linux cheat sheet

Sun, 01 Nov 2026 00:00:00 GMT

Scannable commands for systemd, journals, files, processes, packages, users, and networking on Debian—grouped for quick lookup beside the Linux operating system series.

Linux distributions and Debian

Sun, 01 Nov 2026 00:00:00 GMT

A distribution turns the Linux kernel into an installable system with policies, packages, and support timelines. This overview explains what distros add, how Debian's stable, testing, and unstable branches work, common derivatives, and how other families compare when you choose a base.

Linux filesystems

Sun, 01 Nov 2026 00:00:00 GMT

Paths, inodes, and mount points organize storage on Linux. This overview covers the Filesystem Hierarchy Standard, hard and symbolic links, common on-disk formats, /etc/fstab, virtual filesystems like /proc and /sys, and swap.

Linux glossary

Sun, 01 Nov 2026 00:00:00 GMT

Terms for the Linux operating system series—kernel, distribution, systemd, inode, namespace, and more—each defined briefly and linked to the chapter that goes deeper.

Linux on Windows, WSL, containers, and VMs

Sun, 01 Nov 2026 00:00:00 GMT

Linux runs on bare metal, inside VMs, in containers on a shared kernel, and on Windows via WSL2. This overview compares isolation and use cases and points to Docker and security chapters elsewhere in the knowledgebase.

Linux security primitives

Sun, 01 Nov 2026 00:00:00 GMT

Beyond file modes, Linux isolates and constrains processes with capabilities, namespaces, cgroups, seccomp, and mandatory access control. This overview explains AppArmor on Debian, SELinux elsewhere, and how containers combine these kernel features.

Loops in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

for-of iterates values; for-in walks enumerable keys and is the wrong default for arrays. Classic for loops with var still show up in legacy code and create closure bugs in callbacks. break, continue, and labels behave like C, with for-await-of added for async iterables.

Managing GraphQL schemas in organizations

Sun, 01 Nov 2026 00:00:00 GMT

Large companies rarely expose one undifferentiated graph. This overview covers public, partner, and internal APIs, schema registries and contracts, CI checks against real operations, ownership, and versioning strategies from continuous evolution to dated releases.

Map and WeakMap

Sun, 01 Nov 2026 00:00:00 GMT

Map and WeakMap associate keys with values when object identity or garbage collection behavior matters more than string property names. This page compares APIs, iteration, and typical use cases next to plain objects and Set.

Memory management and garbage collection

Sun, 01 Nov 2026 00:00:00 GMT

JavaScript gives you no way to free memory, only ways to stop referring to it. This chapter explains what the heap holds, how a tracing collector decides what is garbage, why V8 splits the heap into generations, how heap limits and weak references work, and why cleanup of files and sockets cannot be left to the collector.

Merging versus rebasing

Sun, 01 Nov 2026 00:00:00 GMT

Merge and rebase both integrate branch work, but they rewrite history differently—one adds merge commits, the other replays commits on a new base. Compare fast-forward merges, conflict resolution, squash merges, interactive rebase, and when each approach fits a team.

Middleware in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

Middleware is the first code a NestJS request meets, and the only stage that runs before Nest knows which handler will answer. This chapter covers class and function middleware, binding it to routes in a module, global middleware, and the jobs that belong in a later stage instead.

Modules in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

A NestJS module is the unit that decides which classes exist, which ones other parts of the app may use, and what it depends on. This chapter covers the root and feature modules, exports and imports, shared and re-exported modules, and the narrow case for global modules.

MongoDB Aggregation Framework

Sun, 01 Nov 2026 00:00:00 GMT

Aggregation runs a pipeline of stages that filter, reshape, join, and summarize documents. This chapter covers stage order, grouping and lookups, facets, window functions, writing results with merge or out, views, typed pipelines in TypeScript, memory limits, and why server-side JavaScript stages should be avoided.

MongoDB cheat sheet

Sun, 01 Nov 2026 00:00:00 GMT

A scannable reference for everyday mongosh commands, query and update operators, aggregation stages, index types, and the Node.js driver methods that implement the same operations—meant to sit beside the MongoDB series.

MongoDB glossary

Sun, 01 Nov 2026 00:00:00 GMT

Terms used across the MongoDB series—from BSON and WiredTiger through replica sets, search indexes, and embeddings—each defined briefly and linked to the chapter that goes deeper.

MongoDB with Mongoose in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

@nestjs/mongoose wraps Mongoose in a dynamic module, so a connection is configured once and models are injected like any provider. This chapter connects with settings from ConfigService, defines a schema with decorators, and builds a service around an injected model.

Mongoose with MongoDB

Sun, 01 Nov 2026 00:00:00 GMT

Mongoose adds schemas, validation, middleware, and populate on top of the official driver. This focused chapter explains when an ODM helps, how to type schemas in TypeScript, and how lean queries differ from hydrated documents—without replacing the driver-first approach used elsewhere.

NestJS glossary

Sun, 01 Nov 2026 00:00:00 GMT

The terms used across the NestJS series, from modules and providers through the request lifecycle, configuration, security, and testing. Each entry is a short definition with a link to the chapter that covers it in depth.

Networking on Linux

Sun, 01 Nov 2026 00:00:00 GMT

Sockets and routing are universal; Linux adds interface naming, iproute2, distro-specific network management, systemd-resolved, and netfilter. This overview focuses on the host stack on Debian and points to protocol detail elsewhere in the knowledgebase.

Normalized caching with urql Graphcache

Sun, 01 Nov 2026 00:00:00 GMT

Graphcache stores records and links like a client-side database, enabling mutation updates, optimistic UI, schema-aware keys, and offline replay. This chapter configures @urql/exchange-graphcache for urql 5.

Numbers and BigInt in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

JavaScript numbers are IEEE-754 double-precision values with a safe integer range and familiar binary rounding surprises. BigInt stores arbitrary integers but cannot mix with number in arithmetic without an explicit conversion. This chapter covers literals, safety checks, and when to use each type.

Object types and scalars

Sun, 01 Nov 2026 00:00:00 GMT

Object types model entities with fields; scalars are the leaves that hold concrete values. This chapter covers built-in and custom scalars, enums, lists and non-null markers, interfaces, unions, and the __typename field clients use for polymorphism.

Objects in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

Plain objects are string-keyed maps with a prototype chain, not fixed structs like C structs or Java POJOs. Literals, property access, shorthand, computed keys, and references versus copies set the baseline for everything else in this series.

Operators in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

Beyond familiar arithmetic and comparison, JavaScript adds nullish coalescing, optional chaining, and logical assignment operators that behave differently from || and && in other languages. Precedence tables from C do not fully apply; this page covers the operators that change control flow and defaulting logic.

Package management on Debian

Sun, 01 Nov 2026 00:00:00 GMT

Debian ships software as signed .deb packages installed and upgraded with dpkg and APT. This overview covers repositories, suite components, deb822 sources, backports, pinning, security updates, and Flatpak and Snap beside the system package set.

Pagination in MongoDB

Sun, 01 Nov 2026 00:00:00 GMT

Listing large collections page by page needs a strategy that stays fast as offsets grow and stays stable when rows are inserted or deleted. This chapter compares offset pagination with keyset cursors, total counts, and a typed paginate helper in TypeScript.

Pipes and validation in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

Pipes are the last stage before a NestJS handler runs, and they see each argument on its own. This chapter covers the built-in parsing pipes, request validation with ValidationPipe and class-validator, writing a custom pipe, and where pipes should be bound.

Pitfalls when updating a GraphQL backend

Sun, 01 Nov 2026 00:00:00 GMT

Schema changes that look safe on paper still break mobile clients, caches, and federation. This troubleshooting guide lists common symptoms, root causes, and fixes—from nullability shifts to persisted queries and deploy order.

Processes and inter-process communication

Sun, 01 Nov 2026 00:00:00 GMT

Programs run as processes created by fork and exec, coordinated with signals and IPC. This overview covers the process tree, states, pipes, sockets, shared memory, and D-Bus on Linux—with links to shell and Node boundaries covered elsewhere in the knowledgebase.

Products and prices in Stripe

Sun, 01 Nov 2026 00:00:00 GMT

Products describe what you sell; Prices say how much and how often. Prices are immutable, so catalog changes mean new Price objects. This chapter covers one-time and recurring prices, lookup keys, and seeding a catalog from Node.js.

Promises in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

A Promise represents one eventual result—fulfilled or rejected—and gives shared combinators for sequencing and racing async work. This chapter covers construction, then/catch/finally, Promise.all, and common pitfalls.

Protecting services with Cloud Armor

Sun, 01 Nov 2026 00:00:00 GMT

Cloud Armor attaches WAF rules and rate limits to Google Cloud external load balancers. This chapter fronts the series Cloud Run service with an HTTPS load balancer and a security policy.

Prototypes and inheritance

Sun, 01 Nov 2026 00:00:00 GMT

JavaScript links objects through prototypes, not class tables copied at compile time. Property lookup walks the chain; methods live on shared prototype objects—similar in spirit to Ruby modules, unlike Java subclass field layout.

Providers and dependency injection in NestJS

Sun, 01 Nov 2026 00:00:00 GMT

Providers hold the work of a Nest application, and the injector decides when to create them and who receives them. This chapter shows how the injector resolves a dependency by token, the four kinds of custom provider, injection scopes, and how to break a circular dependency.

Proxy and Reflect

Sun, 01 Nov 2026 00:00:00 GMT

Proxy wraps an object and intercepts get, set, and other operations— validation, logging, reactivity, and virtual properties. Reflect mirrors those operations as functions for consistent defaults in traps.

Pull requests with and without GitHub

Sun, 01 Nov 2026 00:00:00 GMT

Review and integrate changes through pull requests on GitHub—or through email patches and git request-pull when no host is involved. Covers forks, the PR lifecycle, merge strategies, branch protection, and the gh CLI.

Regular expressions in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

RegExp matches patterns in strings—literals, flags, groups, and common String methods. This page summarizes syntax and API surface, including modern named groups and the RegExp.escape helper from recent editions.

Replica sets in MongoDB

Sun, 01 Nov 2026 00:00:00 GMT

A replica set copies data across multiple mongod processes for redundancy and automatic failover. This chapter explains primary and secondary roles, elections, a local three-node Docker Compose layout, read preferences, write concern, and replica set connection strings.

The NestJS request lifecycle

Sun, 01 Nov 2026 00:00:00 GMT

Between the socket and your route handler, a NestJS request passes through middleware, guards, interceptors, and pipes, and exception filters wait for anything that goes wrong. This overview shows the order, what each stage is for, and how global, controller, and route bindings stack.

Resolvers and execution

Sun, 01 Nov 2026 00:00:00 GMT

Resolvers connect schema fields to data sources. This chapter explains the four resolver arguments, default resolvers, parallel query execution, per- request context, the N+1 problem, DataLoader, and how errors bubble through nullable fields.

Routing in Astro

Sun, 01 Nov 2026 00:00:00 GMT

Astro maps files in src/pages to URLs. This page covers static and dynamic routes, getStaticPaths, rest parameters, endpoints that return JSON or feeds, redirects, custom error pages, and the precedence rules that decide which file wins when several match.

Scheduling tasks with cron and systemd timers

Sun, 01 Nov 2026 00:00:00 GMT

Linux runs recurring and one-shot jobs through several schedulers. This overview compares cron and crontab syntax, anacron, systemd timers, and at, and explains when each fits on a typical Debian server or desktop.

Schema design in GraphQL

Sun, 01 Nov 2026 00:00:00 GMT

Good GraphQL schemas mirror how clients use data, not how tables are joined. This chapter covers query-driven design, naming and nullability, Relay-style connections, mutation payloads, and modeling errors as typed results versus the top-level errors array.

Schema design in MongoDB

Sun, 01 Nov 2026 00:00:00 GMT

Flexible schemas speed up early product work but query patterns still need deliberate shape. This chapter compares embedding and referencing, common modeling patterns, anti-patterns, the 16 MB document limit, and optional JSON Schema validation at the collection level.

Schemas and SDL

Sun, 01 Nov 2026 00:00:00 GMT

A GraphQL schema is the contract between client and server: types, fields, and root operations written in Schema Definition Language or generated from code. This chapter explains SDL syntax, the Query/Mutation/Subscription roots, schema-first versus code-first workflows, and introspection.

Scope and closures

Sun, 01 Nov 2026 00:00:00 GMT

Lexical scope decides which bindings are visible where; closures keep outer variables alive after the outer function returns. If you know block scope from C#, Java, or Rust, JavaScript's var hoisting and function closures are the pieces that differ most.

Securing GraphQL APIs

Sun, 01 Nov 2026 00:00:00 GMT

A single /graphql endpoint concentrates power and risk. This overview maps GraphQL-specific threats—introspection, deep queries, alias abuse, CSRF, and verbose errors—to controls you should layer at the gateway and in resolvers.

Server rendering in Astro

Sun, 01 Nov 2026 00:00:00 GMT

Static output is the default, but any route can render on demand once an adapter is installed. This page covers prerendering per route, adapters, request data and cookies, middleware with locals, actions for forms, and typed environment variables.

Strings and template literals in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

JavaScript strings are immutable sequences of UTF-16 code units, not full Unicode code points. Template literals add interpolation, multiline text, and tagged functions. This chapter covers creation, indexing, iteration, and common Unicode pitfalls.

Stripe API keys and the Node.js SDK

Sun, 01 Nov 2026 00:00:00 GMT

Publishable keys belong in the browser, secret and restricted keys stay on the server, and every call goes through a Stripe client instance. This chapter shows how to wire the official stripe npm package into Express, pin an API version, and handle idempotency and errors safely.

Stripe beyond payments

Sun, 01 Nov 2026 00:00:00 GMT

Checkout and subscriptions cover most SaaS needs, but Stripe also runs marketplaces, tax, fraud tools, invoicing, in-person Terminal, and identity checks. This overview names each product so you know what to reach for next without duplicating Stripe's full documentation.

Stripe cheat sheet

Sun, 01 Nov 2026 00:00:00 GMT

Commands and API calls you reach for daily when integrating Stripe with Node.js: CLI forwarding, test cards, key prefixes, and stripe-node snippets grouped by object. Use with the narrative chapters when you need a quick lookup.

Stripe glossary

Sun, 01 Nov 2026 00:00:00 GMT

Terms used across the Stripe series—from Customer and Price through PaymentIntent, Checkout Session, webhook Events, and Connect—each defined briefly and linked to the chapter that goes deeper.

Subscriptions in Stripe

Sun, 01 Nov 2026 00:00:00 GMT

Subscriptions bill Customers on a recurring Price, generate Invoices, and change state over time. This chapter uses Checkout in subscription mode, syncs access through webhooks, and touches upgrades, trials, and the Customer Portal.

Symbols in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

A symbol is a unique, immutable primitive used as a property key that will not collide with string keys or other libraries. Well-known symbols customize built-in behavior. This chapter covers creation, registry symbols, and where symbols show up in everyday APIs.

Terminals and shells in Linux

Sun, 01 Nov 2026 00:00:00 GMT

A terminal is a character device; a shell is a program that interprets commands. This overview covers TTYs, PTYs, virtual consoles, terminal emulators, login versus interactive shells, dash as /bin/sh, and where Bash scripting is documented separately.

Terraform cheat sheet

Sun, 01 Nov 2026 00:00:00 GMT

Scannable Terraform CLI commands for init, fmt, validate, plan, apply, state, import, workspaces, and common environment variables—grouped for quick lookup beside the Terraform series.

Terraform glossary

Sun, 01 Nov 2026 00:00:00 GMT

Terraform terms used across the series—provider, state, backend, plan, drift, and more—each defined briefly and linked to the chapter that explains the idea in depth.

Terraform modules

Sun, 01 Nov 2026 00:00:00 GMT

Modules bundle resources into reusable units with inputs and outputs. This page covers root versus child modules, calling modules from local paths, git, and the Registry, versioning with terraform-google-modules, and refactoring with moved blocks.

Terraform vs OpenTofu and alternatives

Sun, 01 Nov 2026 00:00:00 GMT

Terraform is not the only way to define infrastructure. This comparison covers OpenTofu as a compatible fork, Pulumi's general-purpose languages, cloud-native tools on GCP AWS and Azure, and Ansible for configuration after provisioning.

Testing NestJS applications

Sun, 01 Nov 2026 00:00:00 GMT

Dependency injection is what makes a NestJS app easy to test: any provider can be swapped for a fake before the module is compiled. This chapter covers unit tests with the testing module, overriding providers and guards, and end-to-end tests that send real HTTP requests with supertest.

The event loop, tasks, and microtasks

Sun, 01 Nov 2026 00:00:00 GMT

The event loop is what turns one thread into a responsive program: it picks a task, runs it to completion, drains the microtasks, and gives the browser a chance to render. This chapter walks one turn of the loop, predicts the output of ordering puzzles from first principles, and shows where Node's loop differs.

The Linux kernel

Sun, 01 Nov 2026 00:00:00 GMT

The kernel is the privileged core that talks to hardware and exposes system calls to programs. This overview separates kernel space from user space, explains monolithic design and loadable modules, and covers scheduling, memory, versions, and how Debian ships kernel packages.

The this keyword

Sun, 01 Nov 2026 00:00:00 GMT

this is not lexical like most variables—it is set when a function runs. Call site, method syntax, bind/call/apply, arrow functions, and classes each follow rules that differ from Python's self or Java's implicit receiver.

Transactions in MongoDB

Sun, 01 Nov 2026 00:00:00 GMT

Single-document updates are atomic; multi-document business rules need sessions and transactions on a replica set. This chapter covers withTransaction, read and write concern inside transactions, limits, and when schema design removes the need for cross-collection locks.

Type coercion and equality in JavaScript

Sun, 01 Nov 2026 00:00:00 GMT

Operators and built-ins convert operands when types do not match. Loose equality runs a long conversion pipeline; strict equality compares type and value without coercion. This chapter maps the rules that explain surprising console output.

Typed arrays and ArrayBuffer

Sun, 01 Nov 2026 00:00:00 GMT

Typed arrays view raw bytes in an ArrayBuffer as integers or floats—used by WebGL, audio, binary protocols, and WASM interop. This page explains buffers, views, endianness, and how they differ from normal JavaScript arrays.

Typed operations with GraphQL Codegen

Sun, 01 Nov 2026 00:00:00 GMT

GraphQL Codegen client-preset generates typed document nodes and React hooks from .graphql files and your schema. This runbook configures codegen.ts, the graphql() helper, fragment masking, watch mode, and optional persisted operation hashes.

Undoing and moving changes

Sun, 01 Nov 2026 00:00:00 GMT

Stash work in progress, amend the last commit, reset or restore files, revert published history safely, undo merges, and cherry-pick fixes onto other branches—without guessing which Git area each command touches.

Users, groups and permissions in Linux

Sun, 01 Nov 2026 00:00:00 GMT

Every process runs as a user with group memberships and file mode bits. This overview covers UIDs and GIDs, passwd and shadow, rwx and umask, special bits, ACLs, sudo, and PAM on Debian.

Variables and declarations

Sun, 01 Nov 2026 00:00:00 GMT

Three declaration keywords—var, let, and const—interact with hoisting and the temporal dead zone in ways that differ from block-scoped languages like Java or Rust. const only freezes the binding, not deep object contents. This chapter is the reference for choosing among them in modern code.

Vector search and embeddings in MongoDB

Sun, 01 Nov 2026 00:00:00 GMT

Semantic search stores embedding vectors next to documents and finds nearest neighbors with $vectorSearch. This chapter generates embeddings through Voyage AI, defines vector indexes on Atlas, runs hybrid queries with $rankFusion, and sketches a small RAG retrieval function in TypeScript.

Webhooks in Stripe

Sun, 01 Nov 2026 00:00:00 GMT

Webhooks deliver signed Event objects when payments and subscriptions change. Your Express handler verifies signatures, stays idempotent, and fulfills orders there—not on the success page. This chapter covers routing, key events, and local testing with the Stripe CLI.

What is Astro

Sun, 01 Nov 2026 00:00:00 GMT

Astro renders pages to HTML on the server and ships JavaScript only for the components that need it. This overview explains the islands model, the kind of site Astro is built for, how the project got here, and when another framework is the better choice.

What is Google Cloud Platform?

Sun, 01 Nov 2026 00:00:00 GMT

Google Cloud Platform is a suite of managed services for compute, storage, networking, and operations, scoped to projects inside an organization. This overview explains the resource hierarchy, regions, billing, and how to install the Cloud SDK so later chapters can deploy one small container app.

What is GraphQL

Sun, 01 Nov 2026 00:00:00 GMT

GraphQL is a typed query language for APIs: clients describe the shape of the data they need, and the server returns JSON that matches. This overview covers how requests flow from parse to execution, how responses differ from REST, and when a GraphQL layer is worth the complexity.

What is NestJS

Sun, 01 Nov 2026 00:00:00 GMT

NestJS is a TypeScript framework that gives a Node.js server a fixed architecture: modules, controllers, and providers, wired together by dependency injection. This overview shows what it adds on top of Express or Fastify, how a project starts, and when the structure is worth it.

What is Stripe?

Sun, 01 Nov 2026 00:00:00 GMT

Stripe sits between your web application, your server, and the card networks: it stores customers and catalog data, runs Checkout or custom payment flows, and notifies your backend through webhooks. This overview maps the main API objects and test environments before you write integration code.

Working with remotes

Sun, 01 Nov 2026 00:00:00 GMT

Clone a repository, add a remote, fetch and push commits, and set upstream tracking branches—the mechanics of sharing history with GitHub or any Git server, plus pitfalls when pulling or force-pushing with teammates.

Writing GraphQL operations

Sun, 01 Nov 2026 00:00:00 GMT

Operations are the queries, mutations, and subscriptions clients send. This chapter covers operation names, variables, aliases, reusable fragments, inline fragments for unions, and @include/@skip—patterns you will use in urql and codegen-backed apps.

A short history of Artificial Intelligence

Sat, 31 Oct 2026 00:00:00 GMT

Artificial intelligence did not start with chatbots. It went through decades of bold predictions, two funding collapses, and a slow shift from hand-written rules to learning from data. This overview follows that path from the 1940s to the language models of the late 2010s.

Agentic AI

Sat, 31 Oct 2026 00:00:00 GMT

A chat assistant answers. An agent acts: it plans, calls tools, reads the results, and keeps going until a goal is reached. This overview explains the agent loop, tools, and the harness around the model, how agents evolved since 2022, and where workflow tools like n8n and personal agents like OpenClaw fit.

AI and data privacy

Sat, 31 Oct 2026 00:00:00 GMT

Every prompt sends data somewhere. This overview follows that data: where it goes, how long it is kept, whether it trains future models, and what data protection law requires. It ends with practical rules for people and companies that want to use AI without leaking personal or confidential information.

AI basic concepts

Sat, 31 Oct 2026 00:00:00 GMT

Model, training, token, prompt, context window, hallucination: a small set of terms explains most of what is said about AI. This overview defines each one in plain language and shows how they fit together, without math and without a specific product in mind.

AI glossary

Sat, 31 Oct 2026 00:00:00 GMT

A reference of the terms that come up when people talk about AI, from token and context window to harness, RAG, and alignment. Each entry gives a short definition and points to the article in this collection that explains the idea in more depth.

AI in software development

Sat, 31 Oct 2026 00:00:00 GMT

Software development changed faster with AI than almost any other kind of work. This overview follows the path from code completion to chat in the editor and autonomous coding agents, and covers what the tools do well, where they fail, and the habits that keep AI-written code trustworthy.

AI regulation

Sat, 31 Oct 2026 00:00:00 GMT

Governments regulate AI in very different ways. The EU has a single law that sorts AI by risk, the United States relies on executive orders and state laws, and China regulates specific services. This overview explains the main approaches as of late 2026 and what they mean for companies that build or use AI.

AI safety and risks

Sat, 31 Oct 2026 00:00:00 GMT

The risks of AI range from a chatbot inventing a fact to fears about systems that people can no longer control. This overview sorts the risks into groups, explains each in plain terms, and describes what companies, governments, and users do about them, including the open debate about human-level AI.

AI versus non-AI

Sat, 31 Oct 2026 00:00:00 GMT

A traditional program follows rules a developer wrote. An AI system follows rules it learned from examples, or instructions written in plain language. This comparison shows what that changes for correctness, testing, cost, and failure, and when each approach is the right one.

Evaluating AI models

Sat, 31 Oct 2026 00:00:00 GMT

Every new model claims top scores. This overview explains what benchmarks and leaderboards actually measure, why their numbers need care, and how to build a small evaluation of your own that answers the question that matters: is this model good enough for my task?

Frontier AI companies

Sat, 31 Oct 2026 00:00:00 GMT

A handful of companies build the most capable AI models, and a few more supply the chips and data centers those models run on. This overview sorts the leading companies by the role they play, names their main products, and explains how the layers depend on each other.

Generative AI beyond text

Sat, 31 Oct 2026 00:00:00 GMT

The same advances that produced chat assistants also generate images, speech, music, and video. This overview explains how each kind of media is generated, what the tools are used for, and the questions they raise about copyright, consent, and telling real content from generated content.

How large language models are built

Sat, 31 Oct 2026 00:00:00 GMT

A chat assistant is the end of a long pipeline: collecting text, training a model to predict the next token, teaching it to follow instructions, aligning it with human preferences, and testing it before release. This article walks through each stage and what it adds to the finished model.

Open-weight versus closed models

Sat, 31 Oct 2026 00:00:00 GMT

You can rent a model through a provider's API or download open weights and run the model yourself. This comparison explains what "open" really means for AI models, how the two options differ in capability, cost, privacy, and control, and when each one is the better choice.

pnpm

Sat, 31 Oct 2026 00:00:00 GMT

pnpm keeps one copy of each dependency file and links it into every project that needs it. This page explains that layout, how it compares with npm, Yarn, and Bun, and the commands you run day to day.

Prompting fundamentals

Sat, 31 Oct 2026 00:00:00 GMT

The same model can give a vague answer or an excellent one, depending on what it is told. This overview covers what makes a prompt work: a clear task, enough context, examples, a defined output, and a habit of testing and revising, plus why context matters more as models get stronger.

Retrieval-augmented generation explained

Sat, 31 Oct 2026 00:00:00 GMT

A language model only knows its training data. Retrieval-augmented generation looks up relevant passages in your own documents and hands them to the model with the question. This article explains the indexing and query steps, where RAG systems go wrong, and how RAG compares with fine-tuning and long context windows.

The cost of AI

Sat, 31 Oct 2026 00:00:00 GMT

AI has a price at every level: per token for a developer, per month for a user, billions for a training run, and terawatt-hours for the power grid. This overview explains where the money and energy go, why prices per task keep falling while total spending rises, and how to keep your own costs under control.

Yarn

Sat, 31 Oct 2026 00:00:00 GMT

Yarn keeps one zip of each package and, by default, points Node at those zips instead of copying them into node_modules. This page explains that layout, how it compares with npm, pnpm, and Bun, and the commands you run day to day.

Foundation Model Providers (LLMs & APIs): Companies, Models, and Use Cases

Wed, 25 Mar 2026 00:00:00 GMT

Using a language model in your own software means picking a provider, a model family, and a way to call it. This page explains the ways to access models, how an API call and its pricing work, which providers offer which model families, and how to match a model to a use case.

Code Execution Boundaries in Node.js: CLI, Modules, HTTP, RPC, and Process Isolation

Sun, 08 Mar 2026 00:00:00 GMT

Modern Node.js applications expose functionality through many different invocation mechanisms. A piece of business logic might be executed directly inside the process, triggered through an HTTP…

VPC networks in Google Cloud

Sun, 08 Mar 2026 00:00:00 GMT

A VPC network is your private address space in GCP: subnets, routes, firewalls, NAT, and peering. This chapter maps those pieces on Google Cloud, including Direct VPC egress for Cloud Run.

Mastering JSON in Bash: A Practical Guide to jq

Fri, 06 Mar 2026 00:00:00 GMT

APIs and CLI tools often print JSON. jq filters, formats, and reshapes that output on the pipe without loading it into an editor — this guide walks through the filters you reach for daily in Bash.

Infrastructure as Code with Terraform

Fri, 27 Feb 2026 00:00:00 GMT

Terraform lets you describe cloud infrastructure in version-controlled configuration and reconcile it with a plan/apply loop. This overview covers why IaC matters, how Terraform's declarative model works, the core moving parts, the standard workflow, and authenticating to Google Cloud.

State data in Terraform

Fri, 27 Feb 2026 00:00:00 GMT

Terraform state maps configuration to real resource IDs and attributes. This page explains what state contains, local versus GCS backends with locking, state commands, import and moved blocks, drift, sensitive values, workspaces, and when to use remote state data sources.

Typical errors that occur when module types mismatch

Thu, 09 Oct 2025 00:00:00 GMT

The following error indicates that you are attempting to use the require() statement to import an ECMAScript Module (ESM) in a context where CommonJS is expected. This error typically occurs when…

Build-time vs Runtime modules

Tue, 02 Sep 2025 00:00:00 GMT

Let's dive into how module systems behave at build-time vs runtime , and the distinctions between CommonJS (CJS) , ECMAScript Modules (ESM) , and tools like TypeScript and webpack . I’ll go step by…

File extensions for module imports

Tue, 02 Sep 2025 00:00:00 GMT

If you want, I can make a visual map showing all 6 file extensions, what TypeScript sees, and what Node sees , with arrows showing what extension to use in each import. It’s a really handy cheat…

Module interoperability

Tue, 02 Sep 2025 00:00:00 GMT

This articles gives an overview about how the different modules systems can or cannot be used together.

Subpath imports and exports in package.json

Tue, 02 Sep 2025 00:00:00 GMT

Let’s take a look at subpath imports and exports in Node.js , how they interact with TypeScript compiler settings , and what the practical use cases and best practices are.

AMD and UMD

Mon, 18 Nov 2024 00:00:00 GMT

In the world of JavaScript, modularity is key to writing clean, maintainable, and scalable code. Two popular module formats that have emerged to facilitate this are AMD (Asynchronous Module…

CommonJS modules

Mon, 18 Nov 2024 00:00:00 GMT

CommonJS modules have been a foundational part of JavaScript, especially in Node.js, since before ES modules (ESM) were officially adopted. Designed to enable modular and maintainable code, CommonJS…

ES modules

Mon, 18 Nov 2024 00:00:00 GMT

ESM, or ECMAScript Modules, is the official module system introduced in ECMAScript 6 (ES6), also known as ECMAScript 2015. ESM provides a native, standardized way to organize and structure code in…

Modules in Bundlers

Mon, 18 Nov 2024 00:00:00 GMT

The need to specify file extensions in import statements depends on your runtime and compilation environment, and also on whether you are using ES modules (the import syntax) or CommonJS modules…

Authentication Mechanisms in Web Technology: An Overview

Sun, 17 Nov 2024 00:00:00 GMT

To better understand this article, I recommend reading my article on Authentication - Terms and concepts .

Authentication - Terms and concepts

Sun, 17 Nov 2024 00:00:00 GMT

Authentication and authorization are foundational concepts in web security, yet they are often confused.

Network Tunneling

Sun, 21 Jul 2024 00:00:00 GMT

Network tunneling is a technique used to securely transport data from one network to another. It encapsulates the data packets of one protocol (e.g. HTTP) within the packets of another protocol (e.g.…

Testing TypeScript with Jest

Fri, 05 Apr 2024 00:00:00 GMT

Refer to https://jestjs.io/docs/getting-started

Decorators in TypeScript

Thu, 20 Apr 2023 00:00:00 GMT

TypeScript decorators are a way to modify or extend the behavior of classes, methods, or properties in a declarative manner. They are denoted by the @ symbol and are applied using a syntax similar to…

JetBrains IDE shortcuts for effective code navigation

Thu, 20 Apr 2023 00:00:00 GMT

Ctrl + Shift + Backspace : Go back to the previous edited position Ctrl + Shift + E : Display recent code positions Ctrl + B : Go to declaration Ctrl + F12 : Show current file structure F2 : Go to…

Alignment Cheatsheet for CSS and Tailwind

Wed, 29 Mar 2023 00:00:00 GMT

Tailwind’s alignment utilities are the CSS justify and align properties with shorter names. This sheet pairs each utility with the property it sets, whether it moves on the inline or stacking axis, and which boxes it applies to.

A quick introduction to modules

Mon, 20 Feb 2023 00:00:00 GMT

JavaScript uses several module systems in the wild — CommonJS, ESM, and legacy AMD/UMD — each shaped by its host. This introduction maps those systems before the deeper chapters in the JS Modules series.

Yarn link

Mon, 20 Feb 2023 00:00:00 GMT

yarn link is a command that allows you to link a local npm package to your current project. Why is that useful? To consume code of a package you usually simply install the package as a dependency to…

Caching

Wed, 01 Feb 2023 00:00:00 GMT

A cache's primary purpose is to increase data retrieval performance by reducing the need to access the underlying slower storage layer . Trading off capacity for speed, a cache typically stores a…

JWT, JWS, JWE, and JOSE

Wed, 18 Jan 2023 00:00:00 GMT

JOSE is the specification family for signing and encrypting a set of claims in a URL-safe token. This page separates JWT, JWS, JWE, and JWK, shows how the compact forms are assembled, and lists the checks a recipient makes before trusting those claims.

Defining object properties in JavaScript

Wed, 11 Jan 2023 00:00:00 GMT

Object.defineProperty and friends attach data or accessor descriptors with explicit writable, enumerable, and configurable flags—closer to Java Bean descriptors than to a simple field assignment.

Searching in GitHub

Wed, 11 Jan 2023 00:00:00 GMT

GitHub search spans code, paths, commits, issues, and pull requests with qualifiers such as in:file, language, and repo—plus links to the docs when you need the full query syntax.

API Routes and middleware in NextJS

Thu, 15 Dec 2022 00:00:00 GMT

API Routes let you create an API endpoint inside a Next.js app. An endpoint that shall be available at localhost:3000/api/hello must have a file pages/api/hello.js with the following content:

Customizing App, Document and Error Pages in NextJS

Thu, 15 Dec 2022 00:00:00 GMT

Next.js uses the App component to initialize pages. You can override it creating a ./pages/_app.js file if, for example. you want to do some of the following things:

Deploying a NextJS app

Thu, 15 Dec 2022 00:00:00 GMT

next build builds the production application in the .next folder. After building, next start starts a Node.js server that supports hybrid pages , serving both statically generated and server-side…

Environment variables in NextJS

Thu, 15 Dec 2022 00:00:00 GMT

Next.js has built-in support for loading environment variables from .env.local into process.env .

Handling images and other assets in NestJS

Thu, 15 Dec 2022 00:00:00 GMT

Files inside public can be referenced from the root of the application. That is useful to serve static assets like robots.txt and images. For example, if you add an image to public/me.png , the…

Next CLI

Thu, 15 Dec 2022 00:00:00 GMT

// Start the application in development mode (hot-code reloading, error reporting, etc) next dev next dev mydir -p 8080 // build application in current directory's .next folder next build next build…

Pages, Routing and Navigation in NextJS

Thu, 15 Dec 2022 00:00:00 GMT

In Next.js, a page is a React Component exported from a file ( .js , .jsx , .ts , or .tsx ) in the pages directory . The component can have any name, but you must export it as a default export.

Rendering and data fetching in NextJS

Thu, 15 Dec 2022 00:00:00 GMT

Each generated HTML is associated with minimal JavaScript code necessary for that page. When a page is loaded by the browser, its JavaScript code runs and makes the page fully interactive. This…

Installing NextJS

Thu, 15 Dec 2022 00:00:00 GMT

As of december 2022 you need node version 14.6 or later to run NextJS.

Styling in NextJS

Thu, 15 Dec 2022 00:00:00 GMT

Next.js allows several possibilities for styling:

Testing with Jest in NextJS for TypeScript

Thu, 15 Dec 2022 00:00:00 GMT

Add to package.json :

Using NextJS with TypeScript

Thu, 15 Dec 2022 00:00:00 GMT

Create an empty tsconfig.json file in the root of your project and add dependencies:

Semantic Versioning

Sun, 13 Nov 2022 00:00:00 GMT

A version of 3.6.12 means

Docker networking

Wed, 09 Nov 2022 00:00:00 GMT

Docker connects containers with bridge networks, veth pairs, and drivers. This page covers compose-style networking; the Linux host stack—iproute2, nftables, and interface naming—is in the Linux networking chapter.

Docker Volumes

Wed, 09 Nov 2022 00:00:00 GMT

Containers have a "scratch space" that allows you to store files only temporarily, meaning as long as the container is running. But once the container stopped the data is gone.

Installing Docker

Wed, 09 Nov 2022 00:00:00 GMT

Docker Toolbox is outdated and I won't describe it in this article, but it used to be the only option for Windows 7/8 users in the past. It includes Docker Client, Docker Compose, Docker Kitematic…

Managing Docker containers

Wed, 09 Nov 2022 00:00:00 GMT

Run docker inspect to check it. The result could be:

Managing Docker images

Wed, 09 Nov 2022 00:00:00 GMT

An image actually consists of many images, aka image layers. The main reasons being that those can be cached and thus don't have to be rebuild every time you create an image.

Debug NextJS with Nx in Jetbrains

Thu, 03 Nov 2022 00:00:00 GMT

Creating a debug session for NextJS within a Nx workspace is not an easy straightforward task as this NX issue shows (after two years the issue is still open). Solutions are mentioned for VSCode, but…

Proxy-, Reverse-Proxy Server and Load Balancer

Wed, 02 Nov 2022 00:00:00 GMT

Client and Proxy are in the same network. If a client wants to communicate with a resource outside of the network, it does not do so directly, but instead asks the proxy to do that. Reasons why that…

REST vs RPC

Wed, 02 Nov 2022 00:00:00 GMT

Representational State Transfer (ReST or REST) follows a structured approach and necessitates that developers clearly organize their resources using universal resource identifiers ( URIs ). REST APIs…

Managing different node version with nvm on Windows

Mon, 31 Oct 2022 00:00:00 GMT

Nvm ( Node Version Manager ) allows you to quickly install and use different versions of node via the command line.

SinonJS with Mocha

Mon, 31 Oct 2022 00:00:00 GMT

Fakes, spies and stubs are created in the default sandbox which needs to be restored after each test to prevent memory leaks. We use a Mocha hook plugin for that:

The concepts of testing

Sun, 30 Oct 2022 00:00:00 GMT

When it comes to speaking how many tests there should be for each test type then you can assume that you will write mostly Unit Tests, a moderate amount of Integration Tests and a relatively small…

Ethernet and Switching

Thu, 27 Oct 2022 00:00:00 GMT

CSMA/CD (Carrier Sense Multiple Access with Collision Detection). In an old fashioned Bus structure all connected devices were listening and sending on the same wire one at a time. If a device…

IP Addressing

Thu, 27 Oct 2022 00:00:00 GMT

Classful Addressing was used mainly before 1995. Today Classless Addressing is used.

IP Routing

Thu, 27 Oct 2022 00:00:00 GMT

IP Routing is all about sending information from one IP address to another. That might sound like a straight forward thing to do, but it gets a bit complicated, because a destination IP address often…

Network topology

Thu, 27 Oct 2022 00:00:00 GMT

There used to be Bus (every device on one wire) and Token Ring by IBM (a token goes around in a ring and visits every device), but today it is mostly a Star topology (many devices connected to a…

Network segmentation

Thu, 27 Oct 2022 00:00:00 GMT

Network segmentation is a fundamental practice in modern network design aimed at enhancing performance, security, and manageability. By dividing a larger network into smaller, isolated segments,…

Error handling in JavaScript

Fri, 21 Oct 2022 00:00:00 GMT

JavaScript has no compile step in the browser: syntax fails at parse time, everything else surfaces at runtime through throw and the Error hierarchy. try/catch/finally, the cause option, custom Error subclasses, and AggregateError cover sync code and Promise rejection paths.

QuickTip: React forwardRef with TypeScript

Sun, 16 Oct 2022 00:00:00 GMT

import {HTMLAttributes, FC, forwardRef} from 'react' interface Props extends HTMLAttributes { } export const PageCover = forwardRef((props, ref) => { return (…

JavaScript Fails

Fri, 14 Oct 2022 00:00:00 GMT

JavaScript will look you in the eye and insist that these results are normal. NaN is a number, 0.1 + 0.2 is not 0.3, and two empty arrays added together become a string. This page keeps each famous expression, the value it produces, and the rule that makes the despair official.

Commands and tasks in NX

Mon, 10 Oct 2022 00:00:00 GMT

In NX a command represents something like nx run header:build , whereas build is the target , header is the project and header:build is the task .

Apps and libs with NX

Mon, 10 Oct 2022 00:00:00 GMT

There are many different kinds of applications you can create, such as React, Angular, Express, Node etc. Nx is lets you add those via plugins. If you create your first workspace then you can…

Setting up a workspace in Nx

Mon, 10 Oct 2022 00:00:00 GMT

A monorepo is a version-controlled code repository that holds many projects. While these projects may be related, they are often logically independent and run by different teams. NX is a build…

Updating Nx and its dependencies

Mon, 10 Oct 2022 00:00:00 GMT

Updating to the latest version of Nx involves these steps.

Using Nx with Jetbrains IDE

Mon, 10 Oct 2022 00:00:00 GMT

Here is how you have to configure Jetbrains IDE to make Jest work within a NX workspace. When I say "work" I mean to make it possible that Jetbrains UI is used to visually indicate failed and…

Async generator in TypeScript

Wed, 05 Oct 2022 00:00:00 GMT

TypeScript types async generators with AsyncGenerator, AsyncIterable, and AsyncIterator so yield and for await..of stay checked at compile time. This page covers return types, TReturn/TNext, and typing consumers.

Module resolution deep-dive

Wed, 05 Oct 2022 00:00:00 GMT

or Non-relatively:

QuickTip: Automatically switch light and dark mode in Windows

Wed, 05 Oct 2022 00:00:00 GMT

Install Auto Dark Mode from https://github.com/AutoDarkMode/Windows-Auto-Night-Mode by using a command prompt with administrative rights and then run:

Symbols in TypeScript

Wed, 05 Oct 2022 00:00:00 GMT

TypeScript treats symbol keys as a distinct property kind with unique typing rules. This page shows how to declare symbol properties, narrow objects that carry them, and avoid accidental string-key collisions in typed APIs.

Type Guards in TypeScript

Wed, 05 Oct 2022 00:00:00 GMT

Type Guards are used to check whether you are dealing with a certain type or not. Getting from a more general type to a more specific type is called Narrowing . There are different ways to 'type…

TypeScript installation and configuration

Wed, 05 Oct 2022 00:00:00 GMT

Now you can use the TypeScript compiler running tsc . To test whether a TypeScript file compiles create a simple file:

Utility Types in TypeScript

Wed, 05 Oct 2022 00:00:00 GMT

Utility types let you create types based on other types. Have a look at the official TypeScript page for example about utility types.

Resetting Windows files and folder permissions

Mon, 03 Oct 2022 00:00:00 GMT

Open the command prompt with administrative rights, then run one of these:

Scan and fix corrupted Windows system files

Mon, 03 Oct 2022 00:00:00 GMT

Start a command prompt with administrative privileges, then run

Set in JavaScript

Wed, 28 Sep 2022 00:00:00 GMT

A Set stores unique values using SameValueZero equality—handy for deduplication, membership tests, and set algebra. This page covers construction, iteration, and the native union/intersection helpers added in ES2025.

QuickTip: Force a non-empty array in TypeScript

Fri, 01 Apr 2022 00:00:00 GMT

This is how you can force TypeScript to always have at least one item in an array. Or in other words: to not allow empty arrays.

QuickTip: Grouping React components in surrounding components

Fri, 07 Jan 2022 00:00:00 GMT

Let's assume you have an array of data:

PowerShell

Fri, 05 Nov 2021 00:00:00 GMT

PowerShell is a shell and a scripting language whose pipeline carries objects. This overview explains how that differs from bash, how Windows PowerShell 5.1 and PowerShell 7 relate, where the current release runs, and when a .ps1 script is the right tool.

Testing with Cypress.io 12

Fri, 08 Oct 2021 00:00:00 GMT

Selenium and most other testing tools run outside of the browser and execute remote commands across the network. Cypress does the opposite as it is executed in the same run loop as the application.…

QuickTip: Filter object properties by key

Mon, 12 Jul 2021 00:00:00 GMT

Pick or drop keys on a plain object without mutating the original—destructuring for one key, Object.fromEntries with filter for allowlists.

Firestore with NextJS

Sun, 11 Jul 2021 00:00:00 GMT

Cloud Firestore is a cloud-hosted, NoSQL database that your iOS, Android, and web apps can access directly via native SDKs.

QuickTip: Use useRef to fix React state update on unmounted component

Wed, 26 May 2021 00:00:00 GMT

When React tries to set state on a component that has been unmounted from the DOM you get that error:

React with Recoil state management

Tue, 25 May 2021 00:00:00 GMT

Add RecoilRoot to your root component

React and rerendering

Mon, 24 May 2021 00:00:00 GMT

A functional component will refresh any time it receives new props, more precisely if its old and new props fail a referential identity check.

CSS Flexbox in Tailwind

Sat, 22 May 2021 00:00:00 GMT

Flexbox lays out items in a single row or column and decides where the leftover space goes. This page explains the two axes that every flex class refers to, then walks through Tailwind's direction, alignment, wrapping, and sizing classes with live demos you can change.

QuickTip: Smooth scrolling effect with pure CSS only

Mon, 17 May 2021 00:00:00 GMT

Smooth scrolling effect with pure CSS only, without JavaScript

Google Cloud cheat sheet

Tue, 13 Apr 2021 00:00:00 GMT

Scannable gcloud commands for projects, IAM, Cloud Storage, Artifact Registry, Cloud Run, Cloud Build, logging, and monitoring—grouped for quick lookup beside the Google Cloud Platform series.

Types in TypeScript

Tue, 06 Apr 2021 00:00:00 GMT

Boolean, Number, String, Array, Enum, Void, Null, Undefined, Never, Any.

QuickStart: React with TypeScript

Tue, 06 Apr 2021 00:00:00 GMT

You need Node >= 10.16 and npm >= 5.6 .

Bundling files with Webpack 5

Thu, 25 Feb 2021 00:00:00 GMT

Your application might consist of hundreds of files. To run those files in production you need to optimize them. There are many ways to optimize your source code for production. Webpack is helping…

Google Cloud Storage

Tue, 02 Feb 2021 00:00:00 GMT

Cloud Storage holds object data in buckets with storage classes, lifecycle rules, and IAM. This chapter places GCS next to disks and databases, configures a bucket for the series API, and implements upload and list with the Node.js client.

OSI Model

Fri, 22 Jan 2021 00:00:00 GMT

The OSI model groups network behavior into seven layers for teaching and troubleshooting. This page maps common protocols to those layers; Linux host configuration—interfaces, routing, and firewalls—lives in the Linux networking chapter.

Packaging Kubernetes applications with Helm

Tue, 19 Jan 2021 00:00:00 GMT

What is Helm and why would you need it? What problem does it solve?

Kubernetes Deployments

Mon, 18 Jan 2021 00:00:00 GMT

The word deployment is a bit overloaded with different meanings: A deployment is about getting your application code running on servers. In Kubernetes a Deployment is also the name of a resource or…

Managing Pods in Kubernetes

Mon, 18 Jan 2021 00:00:00 GMT

As mentioned before, a Pod is Kubernetes' most atomic deployable unit. Containers must always be placed within a Pod. A Pod always belongs to one and only one node (which is located at a certain…

Kubernetes Multi-Container Patterns

Mon, 18 Jan 2021 00:00:00 GMT

A classic example of multi container pods is when you have your Main app Container separated from a Container that has helper code. That way you separate responsibility and the Helper Container can…

Kubernetes Networking and Services

Mon, 18 Jan 2021 00:00:00 GMT

Each Pod has its own IP address. Containers within a Pod can communicate with each other via their ports over localhost . But how does one Pod communicate with another? We cannot rely on a Pod's IP…

Docker Compose

Sun, 17 Jan 2021 00:00:00 GMT

The basic idea behind Docker Compose is to save you a lot of typing when creating, configuring, stopping, rebuilding or inspecting your containers. We create a docker-compose,yml file to define our…

Docker overview

Thu, 14 Jan 2021 00:00:00 GMT

Docker packages applications as images and runs them as isolated containers on a shared Linux kernel. This overview covers terminology and workflows; namespaces, cgroups, and when to prefer VMs are in the Linux OS series.

Kubernetes Data Persistence

Wed, 13 Jan 2021 00:00:00 GMT

Here is the assumed prerequisite: Your application runs in Containers. You use Kubernetes for orchestration and know that those Containers are put inside Pods . What your application needs is a way…

Kubernetes Overview

Mon, 11 Jan 2021 00:00:00 GMT

The basic idea behind Kubernetes (aka K8s) is that you declare/describe the desired state of your application infrastructure via a manifest file, for example: "Run 3 nodes in 1 cluster, each…

Shellscripting with Bash

Sat, 17 Oct 2020 00:00:00 GMT

Bash scripts glue commands together with variables, tests, and pipelines. This article is the language and scripting reference; for TTYs, login shells, and why /bin/sh is dash on Debian, see the Linux series terminals chapter.

Testing React Components

Sun, 11 Oct 2020 00:00:00 GMT

We are going to have a look at how you can test your React Components and your Redux reducers and actions.

Testing JavaScript NodeJS files with Mocha and Chai

Sat, 10 Oct 2020 00:00:00 GMT

This article will demonstrate how to test JavaScript files in NodeJS using the libraries Sinon, Mocha and Chai. Sinon is often installed together with Mocha and Chai, but it is not required.

Env vars, process and globals in NodeJS

Mon, 28 Sep 2020 00:00:00 GMT

You can define custom env variables in two ways:

Executing commands and files in NodeJS

Mon, 28 Sep 2020 00:00:00 GMT

There are a couple of ways to execute files and commands, but all use the module child_process .

Load balancing an HTTP server with cluster module

Mon, 28 Sep 2020 00:00:00 GMT

There are many strategies to scale your application:

Event Loop in NodeJS

Mon, 28 Sep 2020 00:00:00 GMT

Slow I/O operations such as accessing disk and network resources are handled via Node's Event Loop . The Event Loop is started once you run a node script and exits once there are no more callbacks to…

File system operations in NodeJS

Mon, 28 Sep 2020 00:00:00 GMT

Node offers both, sync and async methods to handle files. Sync methods (having sync in the method name, e.g. fs.readFileSync() ) will block the execution of the program until it has finished…

NodeJS modules

Mon, 28 Sep 2020 00:00:00 GMT

In the REPL all node modules are already present so you do not have to explicitly require() them first. But when you write your own files you must choose between one of two options:

V8 and the REPL in NodeJS

Mon, 28 Sep 2020 00:00:00 GMT

Node's build-in JavaScript engine is V8, but others such as Chakra (by Microsoft) can be used. V8 has three feature groups:

Streams in NodeJS

Mon, 28 Sep 2020 00:00:00 GMT

Streams are collections of data that might not be available all at once and don't have to fit in memory all at once. For example if you want to serve a file that is 1GB over HTTP you would create a…

Working with HTTP and HTTPS in NodeJS

Mon, 28 Sep 2020 00:00:00 GMT

What you can achieve are things like:

npm - Node Package Manager

Thu, 24 Sep 2020 00:00:00 GMT

A file named package.json allows package management in your project. To create it by answering prompts run npm init , add -y if you want to create it instantly, skipping questions.

Pass by value and reference in JavaScript

Wed, 22 Jul 2020 00:00:00 GMT

Primitives are copied by value; objects are shared by copying a reference to the same identity. Reassigning a binding is not the same as mutating an object. This chapter explains what actually moves when you pass arguments or assign to another variable.

OAuth2 - What it is and how it works

Sun, 24 May 2020 00:00:00 GMT

This article gives a big picture overview on how OAuth2 works

Error handling with async/await in TypeScript

Fri, 15 May 2020 00:00:00 GMT

TypeScript narrows results when you separate success and failure with typed tuples or Result-like helpers, and it types catch clauses under useUnknownInCatchVariables. This page focuses on typing async error paths—not on try/catch mechanics.

Async and defer loading of JavaScript

Sun, 16 Feb 2020 00:00:00 GMT

Classic script tags block HTML parsing while they download and run. The async and defer attributes change when download and execution happen relative to the document, and module scripts follow different rules again.

Azure Compute

Sat, 18 Jan 2020 00:00:00 GMT

This article gives a short overview over the Azure Compute Services

Arrays in JavaScript

Wed, 18 Dec 2019 00:00:00 GMT

Arrays are ordered, indexable lists and the default collection in most JavaScript code. This cheat sheet groups creation, mutation, search, and higher-order methods—including ES2023 non-mutating updates—so you can scan the API without rereading a tutorial.

Generators in JavaScript

Sat, 30 Nov 2019 00:00:00 GMT

Generator functions pause at yield and resume on next(), which makes them the standard way to build iterators without manual state. This chapter covers two-way yield, for..of, yield*, and early completion with return and throw.

Iterators in JavaScript

Wed, 30 Oct 2019 00:00:00 GMT

Iterators expose a uniform way to walk values one step at a time, whether the source is an array, a map, or a custom sequence. This chapter covers the iterator and iterable protocols, for..of, and when manual next() beats a loop.

CSS Transitions and Animations

Mon, 30 Sep 2019 00:00:00 GMT

CSS provides (at least) two ways to set elements in motion: transitions and animations. In this article we compare them and show how they work.

React hooks

Wed, 11 Sep 2019 00:00:00 GMT

React hooks are a new way to enhance your React Functional Components, for example to let them handle state or reference DOM elements. Before hooks were introduced the only way to achieve this was to…

Web Accessibility Guidelines

Thu, 29 Aug 2019 00:00:00 GMT

In this article we take a look at Web Accessibility Guidelines. What they are and when and why you should apply them.

Prompt user for input in Microsoft Bot Framework

Thu, 13 Jun 2019 00:00:00 GMT

In this example we are going to ask the user for name, age and a flight date. The challenge is to validate the input, store it in memory and send prompts to the user until we have all the infos.

JavaScript under the hood

Thu, 06 Jun 2019 00:00:00 GMT

Your code runs inside an engine, the engine runs inside a host, and the host decides when your code runs at all. This overview maps those layers, follows one small program through all of them, and points to the chapter that takes each layer apart.

Managing state with Microsoft Bot Framework

Wed, 24 Apr 2019 00:00:00 GMT

In this article we are going to add state to our bot that we created earlier. We want that our bot asks for our name, remembers it and then greets us using the name. Without state management the bot…

Sending messages and cards in Microsoft Bot Framework

Wed, 17 Apr 2019 00:00:00 GMT

TurnContext provides information to process an incoming activity within Microsoft Bot Framework. In this article we find out how to send messages and files using cards.

Inspecting the generated TypeScript code of the Chatbot

Tue, 16 Apr 2019 00:00:00 GMT

We take a closer look at the files that the Yeoman generator produced for our Chatbot.

Setting up a Chatbot with Microsoft Bot Framework and TypeScript

Fri, 12 Apr 2019 00:00:00 GMT

In this article we will setup a Chatbot that echoes whatever we enter using Microsoft Bot Framework SDK v4 with TypeScript. We will use Yeoman to generate code that we will further enhance in…

Asynchronous data handling

Tue, 09 Apr 2019 00:00:00 GMT

JavaScript runs user code on one thread per realm, yet programs must respond to timers, network I/O, and user input without blocking. This overview maps callbacks, promises, async/await, cancellation, and observables—and when each fits.

Observing element changes with MutationObserver in JavaScript

Tue, 09 Apr 2019 00:00:00 GMT

MutationObserver runs a callback after the DOM changes — attributes, child nodes, or text — without polling. This page shows how to configure observation narrowly so you pay only for the mutations you care about.

Observables in JavaScript

Mon, 01 Apr 2019 00:00:00 GMT

Observables push many values over time and support unsubscribe, which suits events and live streams but adds weight promises avoid. This comparison chapter covers push versus pull, RxJS basics, and when to stay with promises.