tc39 / Proposal Object Rest Spread

Object Rest/Spread Properties for ECMAScript

ECMAScript 6 introduces rest elements for array destructuring assignment and spread elements for array literals.

This proposal introduces analogous rest properties for object destructuring assignment and spread properties for object literals.

Specification

Specification

Rest Properties

Rest properties collect the remaining own enumerable property keys that are not already picked off by the destructuring pattern. Those keys and their values are copied onto a new object.

let { x, y, ...z } = { x: 1, y: 2, a: 3, b: 4 };
x; // 1
y; // 2
z; // { a: 3, b: 4 }

Spread Properties

Spread properties in object initializers copies own enumerable properties from a provided object onto the newly created object.

let n = { x, y, ...z };
n; // { x: 1, y: 2, a: 3, b: 4 }

Transpilers

Babel

JSTransform

TypeScript

Status of this Proposal

It is a Stage 4 proposal for ECMAScript.

Known Issues

This proposal only iterates over own properties. See why this matters.