46 lines
1.5 KiB
JavaScript
46 lines
1.5 KiB
JavaScript
// https://tc39.github.io/ecma262/#sec-array.prototype.find
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if (!Array.prototype.find) {
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Object.defineProperty(Array.prototype, 'find', {
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value: function (predicate) {
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// 1. Let O be ? ToObject(this value).
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if (this == null) {
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throw TypeError('"this" is null or not defined');
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}
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var o = Object(this);
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// 2. Let len be ? ToLength(? Get(O, "length")).
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var len = o.length >>> 0;
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// 3. If IsCallable(predicate) is false, throw a TypeError exception.
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if (typeof predicate !== 'function') {
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throw TypeError('predicate must be a function');
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}
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// 4. If thisArg was supplied, let T be thisArg; else let T be undefined.
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var thisArg = arguments[1];
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// 5. Let k be 0.
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var k = 0;
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// 6. Repeat, while k < len
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while (k < len) {
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// a. Let Pk be ! ToString(k).
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// b. Let kValue be ? Get(O, Pk).
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// c. Let testResult be ToBoolean(? Call(predicate, T, « kValue, k, O »)).
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// d. If testResult is true, return kValue.
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var kValue = o[k];
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if (predicate.call(thisArg, kValue, k, o)) {
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return kValue;
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}
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// e. Increase k by 1.
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k++;
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}
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// 7. Return undefined.
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return undefined;
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},
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configurable: true,
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writable: true
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});
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}
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