An ES2019 spec-compliant Array.prototype.flat 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 proposed spec.
Because Array.prototype.flat depends on a receiver (the this value), the main export takes the array to operate on as the first argument.
npm install --save array.prototype.flat
var flat = require('array.prototype.flat'); var assert = require('assert'); var arr = [1, [2], [], 3, [[4]]]; assert.deepEqual(flat(arr, 1), [1, 2, 3, [4]]);
var flat = require('array.prototype.flat'); var assert = require('assert'); /* when Array#flat is not present */ delete Array.prototype.flat; var shimmedFlat = flat.shim(); assert.equal(shimmedFlat, flat.getPolyfill()); assert.deepEqual(arr.flat(), flat(arr));
var flat = require('array.prototype.flat'); var assert = require('assert'); /* when Array#flat is present */ var shimmedIncludes = flat.shim(); var mapper = function (x) { return [x, 1]; }; assert.equal(shimmedIncludes, Array.prototype.flat); assert.deepEqual(arr.flat(mapper), flat(arr, mapper));
Simply clone the repo, npm install, and run npm test