87 lines
2.6 KiB
JavaScript
87 lines
2.6 KiB
JavaScript
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/**
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* @source {https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from#Polyfill}
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* but without thisArg (too hard to type, no need to `this`)
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*/
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var toStr = Object.prototype.toString;
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function isCallable(fn) {
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return typeof fn === "function" || toStr.call(fn) === "[object Function]";
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}
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function toInteger(value) {
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var number = Number(value);
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if (isNaN(number)) {
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return 0;
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}
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if (number === 0 || !isFinite(number)) {
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return number;
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}
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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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function toLength(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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/**
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* Creates an array from an iterable object.
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* @param iterable An iterable object to convert to an array.
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*/
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/**
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* Creates an array from an iterable object.
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* @param iterable An iterable object to convert to an array.
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* @param mapfn A mapping function to call on every element of the array.
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* @param thisArg Value of 'this' used to invoke the mapfn.
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*/
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export default function arrayFrom(arrayLike, mapFn) {
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// 1. Let C be the this value.
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// edit(@eps1lon): we're not calling it as Array.from
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var C = Array;
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// 2. Let items be ToObject(arrayLike).
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var items = Object(arrayLike);
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// 3. ReturnIfAbrupt(items).
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if (arrayLike == null) {
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throw new TypeError("Array.from requires an array-like object - not null or undefined");
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}
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// 4. If mapfn is undefined, then let mapping be false.
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// const mapFn = arguments.length > 1 ? arguments[1] : void undefined;
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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("Array.from: when provided, the second argument must be a function");
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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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// 16. Let k be 0.
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var k = 0;
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// 17. Repeat, while k < len… (also steps a - h)
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var kValue;
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while (k < len) {
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kValue = items[k];
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if (mapFn) {
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A[k] = mapFn(kValue, k);
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} else {
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A[k] = kValue;
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}
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k += 1;
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}
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// 18. Let putStatus be Put(A, "length", len, true).
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A.length = len;
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// 20. Return A.
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return A;
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}
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//# sourceMappingURL=array.from.mjs.map
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