Array.from()

// Arrow function
Array.from(arrayLike, (element) => { /* ... */ } )
Array.from(arrayLike, (element, index) => { /* ... */ } )

// Mapping function
Array.from(arrayLike, mapFn)
Array.from(arrayLike, mapFn, thisArg)

// Inline mapping function
Array.from(arrayLike, function mapFn(element) { /* ... */ })
Array.from(arrayLike, function mapFn(element, index) { /* ... */ })
Array.from(arrayLike, function mapFn(element) { /* ... */ }, thisArg)
Array.from(arrayLike, function mapFn(element, index) { /* ... */ }, thisArg)

Array.from('foo');
// [ "f", "o", "o" ]

const set = new Set(['foo', 'bar', 'baz', 'foo']);
Array.from(set);
// [ "foo", "bar", "baz" ]

const map = new Map([[1, 2], [2, 4], [4, 8]]);
Array.from(map);
// [[1, 2], [2, 4], [4, 8]]

const mapper = new Map([['1', 'a'], ['2', 'b']]);
Array.from(mapper.values());
// ['a', 'b'];

Array.from(mapper.keys());
// ['1', '2'];

// Create an array based on a property of DOM Elements
const images = document.getElementsByTagName('img');
const sources = Array.from(images, image => image.src);
const insecureSources = sources.filter(link => link.startsWith('http://'));

function f() {
  return Array.from(arguments);
}

f(1, 2, 3);

// [ 1, 2, 3 ]

// Using an arrow function as the map function to
// manipulate the elements
Array.from([1, 2, 3], x => x + x);
// [2, 4, 6]

// Generate a sequence of numbers
// Since the array is initialized with `undefined` on each position,
// the value of `v` below will be `undefined`
Array.from({length: 5}, (v, i) => i);
// [0, 1, 2, 3, 4]

// Sequence generator function (commonly referred to as "range", e.g. Clojure, PHP etc)
const range = (start, stop, step) => Array.from({ length: (stop - start) / step + 1}, (_, i) => start + (i * step));

// Generate numbers range 0..4
range(0, 4, 1);
// [0, 1, 2, 3, 4]

// Generate numbers range 1..10 with step of 2
range(1, 10, 2);
// [1, 3, 5, 7, 9]

// Generate the alphabet using Array.from making use of it being ordered as a sequence
range('A'.charCodeAt(0), 'Z'.charCodeAt(0), 1).map(x => String.fromCharCode(x));
// ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"]

// Production steps of ECMA-262, Edition 6, 22.1.2.1
if (!Array.from) {
    Array.from = (function () {
        var symbolIterator;
        try {
            symbolIterator = Symbol.iterator
                ? Symbol.iterator
                : 'Symbol(Symbol.iterator)';
        } catch (e) {
            symbolIterator = 'Symbol(Symbol.iterator)';
        }

        var toStr = Object.prototype.toString;
        var isCallable = function (fn) {
            return (
                typeof fn === 'function' ||
                toStr.call(fn) === '[object Function]'
            );
        };
        var toInteger = function (value) {
            var number = Number(value);
            if (isNaN(number)) return 0;
            if (number === 0 || !isFinite(number)) return number;
            return (number > 0 ? 1 : -1) * Math.floor(Math.abs(number));
        };
        var maxSafeInteger = Math.pow(2, 53) - 1;
        var toLength = function (value) {
            var len = toInteger(value);
            return Math.min(Math.max(len, 0), maxSafeInteger);
        };

        var setGetItemHandler = function setGetItemHandler(isIterator, items) {
            var iterator = isIterator && items[symbolIterator]();
            return function getItem(k) {
                return isIterator ? iterator.next() : items[k];
            };
        };

        var getArray = function getArray(
            T,
            A,
            len,
            getItem,
            isIterator,
            mapFn
        ) {
            // 16. Let k be 0.
            var k = 0;

            // 17. Repeat, while k < len… or while iterator is done (also steps a - h)
            while (k < len || isIterator) {
                var item = getItem(k);
                var kValue = isIterator ? item.value : item;

                if (isIterator && item.done) {
                    return A;
                } else {
                    if (mapFn) {
                        A[k] =
                            typeof T === 'undefined'
                                ? mapFn(kValue, k)
                                : mapFn.call(T, kValue, k);
                    } else {
                        A[k] = kValue;
                    }
                }
                k += 1;
            }

            if (isIterator) {
                throw new TypeError(
                    'Array.from: provided arrayLike or iterator has length more then 2 ** 52 - 1'
                );
            } else {
                A.length = len;
            }

            return A;
        };

        // The length property of the from method is 1.
        return function from(arrayLikeOrIterator /*, mapFn, thisArg */) {
            // 1. Let C be the this value.
            var C = this;

            // 2. Let items be ToObject(arrayLikeOrIterator).
            var items = Object(arrayLikeOrIterator);
            var isIterator = isCallable(items[symbolIterator]);

            // 3. ReturnIfAbrupt(items).
            if (arrayLikeOrIterator == null && !isIterator) {
                throw new TypeError(
                    'Array.from requires an array-like object or iterator - not null or undefined'
                );
            }

            // 4. If mapfn is undefined, then let mapping be false.
            var mapFn = arguments.length > 1 ? arguments[1] : void undefined;
            var T;
            if (typeof mapFn !== 'undefined') {
                // 5. else
                // 5. a If IsCallable(mapfn) is false, throw a TypeError exception.
                if (!isCallable(mapFn)) {
                    throw new TypeError(
                        'Array.from: when provided, the second argument must be a function'
                    );
                }

                // 5. b. If thisArg was supplied, let T be thisArg; else let T be undefined.
                if (arguments.length > 2) {
                    T = arguments[2];
                }
            }

            // 10. Let lenValue be Get(items, "length").
            // 11. Let len be ToLength(lenValue).
            var len = toLength(items.length);

            // 13. If IsConstructor(C) is true, then
            // 13. a. Let A be the result of calling the [[Construct]] internal method
            // of C with an argument list containing the single item len.
            // 14. a. Else, Let A be ArrayCreate(len).
            var A = isCallable(C) ? Object(new C(len)) : new Array(len);

            return getArray(
                T,
                A,
                len,
                setGetItemHandler(isIterator, items),
                isIterator,
                mapFn
            );
        };
    })();
}