134 lines
No EOL
4.5 KiB
JavaScript
134 lines
No EOL
4.5 KiB
JavaScript
if (!Array.from) {
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Array.from = (function () {
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var symbolIterator;
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try {
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symbolIterator = Symbol.iterator
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? Symbol.iterator
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: 'Symbol(Symbol.iterator)';
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} catch (e) {
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symbolIterator = 'Symbol(Symbol.iterator)';
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}
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var toStr = Object.prototype.toString;
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var isCallable = function (fn) {
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return (
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typeof fn === 'function' ||
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toStr.call(fn) === '[object Function]'
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);
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};
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var toInteger = function (value) {
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var number = Number(value);
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if (isNaN(number)) return 0;
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if (number === 0 || !isFinite(number)) return number;
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return (number > 0 ? 1 : -1) * Math.floor(Math.abs(number));
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};
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var maxSafeInteger = Math.pow(2, 53) - 1;
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var toLength = function (value) {
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var len = toInteger(value);
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return Math.min(Math.max(len, 0), maxSafeInteger);
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};
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var setGetItemHandler = function setGetItemHandler(isIterator, items) {
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var iterator = isIterator && items[symbolIterator]();
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return function getItem(k) {
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return isIterator ? iterator.next() : items[k];
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};
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};
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var getArray = function getArray(
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T,
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A,
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len,
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getItem,
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isIterator,
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mapFn
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) {
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// 16. Let k be 0.
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var k = 0;
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// 17. Repeat, while k < len… or while iterator is done (also steps a - h)
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while (k < len || isIterator) {
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var item = getItem(k);
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var kValue = isIterator ? item.value : item;
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if (isIterator && item.done) {
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return A;
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} else {
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if (mapFn) {
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A[k] =
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typeof T === 'undefined'
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? mapFn(kValue, k)
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: mapFn.call(T, kValue, k);
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} else {
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A[k] = kValue;
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}
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}
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k += 1;
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}
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if (isIterator) {
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throw new TypeError(
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'Array.from: provided arrayLike or iterator has length more then 2 ** 52 - 1'
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);
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} else {
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A.length = len;
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}
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return A;
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};
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// The length property of the from method is 1.
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return function from(arrayLikeOrIterator /*, mapFn, thisArg */) {
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// 1. Let C be the this value.
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var C = this;
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// 2. Let items be ToObject(arrayLikeOrIterator).
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var items = Object(arrayLikeOrIterator);
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var isIterator = isCallable(items[symbolIterator]);
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// 3. ReturnIfAbrupt(items).
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if (arrayLikeOrIterator == null && !isIterator) {
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throw new TypeError(
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'Array.from requires an array-like object or iterator - not null or undefined'
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);
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}
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// 4. If mapfn is undefined, then let mapping be false.
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var mapFn = arguments.length > 1 ? arguments[1] : void undefined;
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var T;
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if (typeof mapFn !== 'undefined') {
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// 5. else
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// 5. a If IsCallable(mapfn) is false, throw a TypeError exception.
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if (!isCallable(mapFn)) {
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throw new TypeError(
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'Array.from: when provided, the second argument must be a function'
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);
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}
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// 5. b. If thisArg was supplied, let T be thisArg; else let T be undefined.
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if (arguments.length > 2) {
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T = arguments[2];
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}
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}
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// 10. Let lenValue be Get(items, "length").
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// 11. Let len be ToLength(lenValue).
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var len = toLength(items.length);
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// 13. If IsConstructor(C) is true, then
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// 13. a. Let A be the result of calling the [[Construct]] internal method
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// of C with an argument list containing the single item len.
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// 14. a. Else, Let A be ArrayCreate(len).
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var A = isCallable(C) ? Object(new C(len)) : new Array(len);
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return getArray(
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T,
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A,
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len,
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setGetItemHandler(isIterator, items),
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isIterator,
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mapFn
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);
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};
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})();
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} |