ES2015: Destructuring reference bindings

es2015-destructuring-reference-bindings.js

/**
 * Destructuring reference bindings.
 * 
 * by Dmitry Soshnikov <[email protected]>
 * MIT Style License
 */

// Bindings of a pattern in destructuring may be not only
// simple variables, but any reference types. In the following
// example we use destructuring assignment to swap two elements
// of an array: the pattern bindings are not variable names in
// in case, but references to array elements.

let a = [1, 2, 3];

[a[0], a[a.length - 1]] = [a[a.length - 1], a[0]];

console.log(a); // [3, 2, 1]

// This is similar to initializer part of a `for-in` or `for-of`,
// where we also could use not only variables but other
// references. As an example, unusual properties collector:

let props = [], i = 0;

for (props[i++] in {x: 1, y: 2});

console.log(props); // ['x', 'y']