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59 lines
1.8 KiB
JavaScript
59 lines
1.8 KiB
JavaScript
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// https://stackoverflow.com/a/33106217
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if (typeof String.prototype.startsWith != 'function') {
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String.prototype.startsWith = function (str) {
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return this.indexOf(str) === 0;
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};
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}
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// https://tc39.github.io/ecma262/#sec-array.prototype.includes
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if (!Array.prototype.includes) {
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Object.defineProperty(Array.prototype, 'includes', {
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value: function (searchElement, fromIndex) {
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if (this == null) {
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throw new TypeError('"this" is null or not defined');
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}
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// 1. Let O be ? ToObject(this value).
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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 len is 0, return false.
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if (len === 0) {
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return false;
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}
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// 4. Let n be ? ToInteger(fromIndex).
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// (If fromIndex is undefined, this step produces the value 0.)
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var n = fromIndex | 0;
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// 5. If n ≥ 0, then
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// a. Let k be n.
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// 6. Else n < 0,
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// a. Let k be len + n.
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// b. If k < 0, let k be 0.
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var k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);
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function sameValueZero(x, y) {
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return x === y || (typeof x === 'number' && typeof y === 'number' && isNaN(x) && isNaN(y));
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}
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// 7. Repeat, while k < len
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while (k < len) {
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// a. Let elementK be the result of ? Get(O, ! ToString(k)).
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// b. If SameValueZero(searchElement, elementK) is true, return true.
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if (sameValueZero(o[k], searchElement)) {
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return true;
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}
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// c. Increase k by 1.
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k++;
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}
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// 8. Return false
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return false;
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}
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});
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} |