function from(arrayLike /*, mapFn, thisArg */) {
            // 1. Let C be the this value.
            var C = this;

            // 2. Let items be ToObject(arrayLike).
            var items = Object(arrayLike);

            // 3. ReturnIfAbrupt(items).
            if (arrayLike == null) {
                throw new TypeError('Array.from requires an array-like object - 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);

            // 16. Let k be 0.
            var k = 0;
            // 17. Repeat, while k < len… (also steps a - h)
            var kValue;
            while (k < len) {
                kValue = items[k];
                if (mapFn) {
                    A[k] = typeof T === 'undefined' ? mapFn(kValue, k) : mapFn.call(T, kValue, k);
                } else {
                    A[k] = kValue;
                }
                k += 1;
            }
            // 18. Let putStatus be Put(A, "length", len, true).
            A.length = len;
            // 20. Return A.
            return A;
        }
// The length property of the from method is 1.
The length property of the from method is 1.
The length property of the from method is 1 .
function from(arrayLike ) {
            var C = this;
            var items = Object(arrayLike);
            if (arrayLike == null) {
                throw new TypeError('Array.from requires an array-like object - not null or undefined');
            }
            var mapFn = arguments.length > 1 ? arguments[1] : void undefined;
            var T;
            if (typeof mapFn !== 'undefined') {
                if (!isCallable(mapFn)) {
                    throw new TypeError('Array.from: when provided, the second argument must be a function');
                }
                if (arguments.length > 2) {
                    T = arguments[2];
                }
            }
            var len = toLength(items.length);
            var A = isCallable(C) ? Object(new C(len)) : new Array(len);
            var k = 0;
            var kValue;
            while (k < len) {
                kValue = items[k];
                if (mapFn) {
                    A[k] = typeof T === 'undefined' ? mapFn(kValue, k) : mapFn.call(T, kValue, k);
                } else {
                    A[k] = kValue;
                }
                k += 1;
            }
            A.length = len;
            return A;
        }
function from ( arrayLike ) { var C = this ; var items = Object ( arrayLike ) ; if ( arrayLike == null ) { throw new TypeError ( 'Array.from requires an array-like object - not null or undefined' ) ; } var mapFn = arguments . length > 1 ? arguments [ 1 ] : void undefined ; var T ; if ( typeof mapFn !== 'undefined' ) { if ( ! isCallable ( mapFn ) ) { throw new TypeError ( 'Array.from: when provided, the second argument must be a function' ) ; } if ( arguments . length > 2 ) { T = arguments [ 2 ] ; } } var len = toLength ( items . length ) ; var A = isCallable ( C ) ? Object ( new C ( len ) ) : new Array ( len ) ; var k = 0 ; var kValue ; while ( k < len ) { kValue = items [ k ] ; if ( mapFn ) { A [ k ] = typeof T === 'undefined' ? mapFn ( kValue , k ) : mapFn . call ( T , kValue , k ) ; } else { A [ k ] = kValue ; } k += 1 ; } A . length = len ; return A ; }
The length property of the from method is 1.
The length property of the from method is 1 .
/*, mapFn, thisArg */ // 1. Let C be the this value. // 2. Let items be ToObject(arrayLike). // 3. ReturnIfAbrupt(items). // 4. If mapfn is undefined, then let mapping be false. // 5. else // 5. a If IsCallable(mapfn) is false, throw a TypeError exception. // 5. b. If thisArg was supplied, let T be thisArg; else let T be undefined. // 10. Let lenValue be Get(items, "length"). // 11. Let len be ToLength(lenValue). // 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). // 16. Let k be 0. // 17. Repeat, while k < len… (also steps a - h) // 18. Let putStatus be Put(A, "length", len, true). // 20. Return A.