array.prototype.unshift

An ES spec-compliant Array.prototype.unshift shim/polyfill/replacement that works as far down as ES3.

This package implements the es-shim API interface. It works in an ES3-supported environment and complies with the spec.

Because Array.prototype.unshift depends on a receiver (the “this” value), the main export takes the array to operate on as the first argument.

Engines where this is needed

Note: this list is not exhaustive.

• Safari 10 - 13
• Chrome 48+ (v8 bug)
• node 6+

Example

var unshift = require('array.prototype.unshift');
var assert = require('assert');

var a = [1, 1, 1];
assert.deepEqual(unshift(a, 1, 2), 5);
assert.deepEqual(a, [1, 2, 1, 1, 1]);

var unshift = require('array.prototype.unshift');
var assert = require('assert');
/* when Array#unshift is not present */
delete Array.prototype.unshift;
var shimmed = unshift.shim();
assert.equal(shimmed, unshift.getPolyfill());
assert.equal(shimmed, Array.prototype.unshift);
assert.deepEqual([1, 2, 3].unshift(1, 2, 3), unshift([1, 2, 3], 1, 2, 3));

var unshift = require('array.prototype.unshift');
var assert = require('assert');
/* when Array#unshift is present */
var shimmed = unshift.shim();
assert.equal(shimmed, Array.prototype.unshift);
assert.deepEqual([1, 2, 3].unshift(1, 2, 3), unshift([1, 2, 3], 1, 2, 3));

Tests

Simply clone the repo, npm install, and run npm test