88 lines
3.2 KiB
JavaScript
88 lines
3.2 KiB
JavaScript
/**
|
|
* Copyright © Dave Perrett, Malcolm Jarvis and Artem Vorotnikov
|
|
*
|
|
* This file is licensed under the GPLv2.
|
|
* http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
|
|
*/
|
|
|
|
if (!Array.from) {
|
|
Array.from = (function () {
|
|
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);
|
|
};
|
|
|
|
// The length property of the from method is 1.
|
|
return 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;
|
|
};
|
|
}());
|
|
}
|