| 'use strict'; |
| var bind = require('../internals/bind-context'); |
| var toObject = require('../internals/to-object'); |
| var callWithSafeIterationClosing = require('../internals/call-with-safe-iteration-closing'); |
| var isArrayIteratorMethod = require('../internals/is-array-iterator-method'); |
| var toLength = require('../internals/to-length'); |
| var createProperty = require('../internals/create-property'); |
| var getIteratorMethod = require('../internals/get-iterator-method'); |
| |
| // `Array.from` method implementation |
| // https://tc39.github.io/ecma262/#sec-array.from |
| module.exports = function from(arrayLike /* , mapfn = undefined, thisArg = undefined */) { |
| var O = toObject(arrayLike); |
| var C = typeof this == 'function' ? this : Array; |
| var argumentsLength = arguments.length; |
| var mapfn = argumentsLength > 1 ? arguments[1] : undefined; |
| var mapping = mapfn !== undefined; |
| var index = 0; |
| var iteratorMethod = getIteratorMethod(O); |
| var length, result, step, iterator, next; |
| if (mapping) mapfn = bind(mapfn, argumentsLength > 2 ? arguments[2] : undefined, 2); |
| // if the target is not iterable or it's an array with the default iterator - use a simple case |
| if (iteratorMethod != undefined && !(C == Array && isArrayIteratorMethod(iteratorMethod))) { |
| iterator = iteratorMethod.call(O); |
| next = iterator.next; |
| result = new C(); |
| for (;!(step = next.call(iterator)).done; index++) { |
| createProperty(result, index, mapping |
| ? callWithSafeIterationClosing(iterator, mapfn, [step.value, index], true) |
| : step.value |
| ); |
| } |
| } else { |
| length = toLength(O.length); |
| result = new C(length); |
| for (;length > index; index++) { |
| createProperty(result, index, mapping ? mapfn(O[index], index) : O[index]); |
| } |
| } |
| result.length = index; |
| return result; |
| }; |