An ES2019 spec-compliant Array.prototype.flatMap 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.flatMap 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.flatmap
var flatMap = require('array.prototype.flatmap'); var assert = require('assert'); var arr = [1, [2], [], 3]; var results = flatMap(arr, function (x, i) { assert.equal(x, arr[i]); return x; }); assert.deepEqual(results, [1, 2, 3]);
var flatMap = require('array.prototype.flatmap'); var assert = require('assert'); /* when Array#flatMap is not present */ delete Array.prototype.flatMap; var shimmedFlatMap = flatMap.shim(); var mapper = function (x) { return [x, 1]; }; assert.equal(shimmedFlatMap, flatMap.getPolyfill()); assert.deepEqual(arr.flatMap(mapper), flatMap(arr, mapper));
var flatMap = require('array.prototype.flatmap'); var assert = require('assert'); /* when Array#flatMap is present */ var shimmedIncludes = flatMap.shim(); var mapper = function (x) { return [x, 1]; }; assert.equal(shimmedIncludes, Array.prototype.flatMap); assert.deepEqual(arr.flatMap(mapper), flatMap(arr, mapper));
Simply clone the repo, npm install, and run npm test