Force a non-empty array in TypeScript

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.

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export interface ColorSelectionProps extends HTMLAttributes<HTMLDivElement> {
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  items: [ColorSelectionItem, ...ColorSelectionItem[]]
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}

You can also force it to have at least 2, 3 etc. items:

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export interface ColorSelectionProps extends HTMLAttributes<HTMLDivElement> {
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  items: [ColorSelectionItem, ColorSelectionItem, ...ColorSelectionItem[]]
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}

This came in handy lately when I was implementing a ColorSelection component in React:

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export const ColorSelection: FC<ColorSelectionProps> = ({ items }) => {
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  const [selected, setSelected] = useState<ColorSelectionItem>(items[0])
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  // ...

Having it statically checked is way better than having a runtime check like if items.length > 0.