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.
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 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 }It is a Stage 4 proposal for ECMAScript.
This proposal only iterates over own properties. See why this matters.