Object property count

Note

This feature also contains the Object.keysLength TC39 stage 2 proposal.

Easily retrieve the length of an object’s keys, own property names, and own property symbols.

Type	TC39	CoreJS	Babel	Civet	JS+
Polyfill	✅ Stage 1 View	❌	❌	❌	✅ via Custom

Caution

This TC39 proposal is meant to remove the necessity to allocate an array every time when calling Object.keys(object).length. This polyfill CAN’T solve this problem but it aims to provide a better and future-compatible method to use.

Object.keysLength(object: object): number

Baseline

Returns the number of an object’s enumerable own string-keyed properties. Equivalent to Object.keys(object).length.

Object.keysLength({ a: 1, b: 2, c: 3 }); // → 3
Object.keysLength({}); // → 0

Object.getOwnPropertyNamesLength(object: object): number

Baseline

Returns the number of an object’s own string-keyed properties, including non-enumerable ones. Equivalent to Object.getOwnPropertyNames(object).length.

const obj = Object.defineProperty({}, 'hidden', { value: 1, enumerable: false });
Object.keysLength(obj); // → 0 (non-enumerable excluded)
Object.getOwnPropertyNamesLength(obj); // → 1 (non-enumerable included)

Object.getOwnPropertySymbolsLength(object: object): number

Baseline

Returns the number of an object’s own symbol-keyed properties. Equivalent to Object.getOwnPropertySymbols(object).length.

const sym1 = Symbol('a');
const sym2 = Symbol('b');
const obj = { [sym1]: 1, [sym2]: 2, c: 3 };

Object.getOwnPropertySymbolsLength(obj); // → 2 (only symbols counted)
Object.keysLength(obj); // → 1 (only string keys counted)