Flatten nested arrays in JavaScript

Flattens nested arrays to any depth, recursively.

function flatten(nested) {
  return nested.reduce(
    (flat, item) =>
      flat.concat(Array.isArray(item) ? flatten(item) : item),
    [],
  );
}

Keywords and builtins used here

• Array
• function
• return

The run, in numbers

Lines

7

Characters to type

130

Tokens

42

Three-star pace

90 tpm

At the three-star pace of 90 tokens a minute, this run takes about 28 seconds.

Type this snippet

Step 5 of 10 in Arrays, step 21 of 43 in Language basics.

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