JavaScript · Language basics

Spread syntax

Expands an iterable into a new array, object or argument list without mutating the original.

javascriptRunnable example javascript course

Syntax

[...a, ...b]

Example

Try it

const a = [1, 2];
const b = [3, 4];
const merged = [...a, ...b, 5];
console.log(merged);

Spread copies are shallow. Nested objects are still shared.

Reference pages are the quick answer. The course explains the why, shows the full example and ends with a challenge.