This page follows How ECMAScript is standardized. It is a scan list, not a tutorial. For narrative context, see A short history of JavaScript.
ES5 (2009)
| Addition | Notes |
|---|---|
| Strict mode | "use strict" |
JSON |
parse, stringify |
| Array extras | forEach, map, filter, reduce, … |
| Object methods | keys, seal, freeze, getters/setters |
| Function.prototype.bind | Partial application |
ES2015 (ES6)
| Addition | Notes |
|---|---|
let, const |
Block scope |
| Classes | Syntactic sugar over prototypes |
| Modules | import / export |
| Arrow functions | Lexical this |
| Promises | Built-in async primitive |
Map, Set, WeakMap, WeakSet |
Collections |
| Template literals | `hello ${name}` |
| Destructuring | Arrays and objects |
| Default and rest parameters | function f(a = 1, ...rest) |
| Iterators / generators | function*, yield |
| Symbols | Symbol(), well-known symbols |
for..of |
Iteration protocol |
ES2016
| Addition | Notes |
|---|---|
** |
Exponentiation operator |
Array.prototype.includes |
Like indexOf but with NaN handling |
ES2017
| Addition | Notes |
|---|---|
async / await |
Promise syntax |
Object.entries, Object.values |
Key/value lists |
SharedArrayBuffer, Atomics |
Shared memory (with isolation requirements) |
| String padding | padStart, padEnd |
| Trailing commas in param lists | Syntax only |
ES2018
| Addition | Notes |
|---|---|
| Rest/spread for objects | { ...obj } |
| Async iteration | for await, async generators |
Promise.prototype.finally |
Cleanup hook |
| RegExp improvements | Named groups, lookbehind, dotAll |
ES2019
| Addition | Notes |
|---|---|
Array.prototype.flat, flatMap |
Nested arrays |
Object.fromEntries |
Inverse of entries |
Optional catch binding |
catch { } without (e) |
String.prototype.trimStart/End |
Aliases trimLeft/Right |
Symbol.prototype.description |
Read symbol debug name |
ES2020
| Addition | Notes |
|---|---|
| Optional chaining | obj?.prop, fn?.() |
| Nullish coalescing | a ?? b |
BigInt |
Arbitrary integers |
globalThis |
Cross-environment global |
Dynamic import() |
Promise-based module load |
Promise.allSettled |
Wait for all outcomes |
String.prototype.matchAll |
Iterator of matches |
ES2021
| Addition | Notes |
|---|---|
| Logical assignment | &&=, ||=, ??= |
| Numeric separators | 1_000_000 |
Promise.any |
First fulfillment |
WeakRef, FinalizationRegistry |
Weak lifecycle hooks |
String.prototype.replaceAll |
Global replace without regex |
ES2022
| Addition | Notes |
|---|---|
| Class fields | Public and private # fields |
| Class static blocks | static { } |
Top-level await in modules |
Module scope |
at() on arrays and strings |
Negative indexing |
| RegExp match indices | d flag, indices |
Object.hasOwn |
Safer than hasOwnProperty |
Error cause |
new Error("msg", { cause }) |
ES2023
| Addition | Notes |
|---|---|
| Array find from end | findLast, findLastIndex |
| Immutable array methods | toSorted, toReversed, toSpliced, with |
| Hashbang grammar | #! in scripts |
| Symbols as weak map keys | WeakMap accepts symbols |
ES2024
| Addition | Notes |
|---|---|
ArrayBuffer.prototype.transfer |
Resizable buffers |
Object.groupBy, Map.groupBy |
Group collections |
Promise.withResolvers |
External resolve/reject |
| Well-formed Unicode strings | isWellFormed, toWellFormed |
| Atomics.waitAsync | Async wait on shared memory |
ES2025 (representative)
| Addition | Notes |
|---|---|
| Iterator helpers | Iterator.prototype.map, .filter, … |
| Set methods | union, intersection, difference, … |
| Import attributes | import json from "./x.json" with { type: "json" } |
| RegExp escaping | RegExp.escape for literal fragments |
Editions after publication continue on tc39/proposals. Verify shipping in your target engines before relying on stage-4 syntax in production without transpilation.
Continue with JavaScript under the hood.