arguments Is Not An Array

The arguments object looks like an array but has none of its methods.

In 2026: Still works in non-arrow functions. arguments holds the call's arguments and has a length and numeric indices, but its type is "object" and it has no map, filter or forEach. You convert it with Array.from(arguments) or a rest parameter. Arrow functions have no arguments at all.

Where it came from: arguments is an array-like object, not an array; MDN's arguments page lists what it lacks. MDN ↗

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