array.prototype.flatmap

array.prototype.flatmap

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.

Getting started

npm install --save array.prototype.flatmap

Usage/Examples

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));

Tests

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

Similar packages

Other packages similar to array.prototype.flatmap

lodash.flatten

Lodash's flatten method provides similar functionality to flatMap for flattening arrays, but it does not include mapping. You would need to chain it with map for similar effects, making array.prototype.flatmap more convenient for combined operations.

underscore.js

Underscore.js offers methods like _.flatten and _.map which can be combined to achieve similar results to flatMap. However, like lodash, this requires chaining multiple operations, whereas array.prototype.flatmap integrates both into one method.