78 lines
2.0 KiB
JavaScript
78 lines
2.0 KiB
JavaScript
/**
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* Resolve `isArray` as native or fallback
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*/
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module.exports = Array.prototype.indexOf
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? nativeIndexOf
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: polyfillIndexOf;
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function nativeIndexOf(array, searchElement, fromIndex) {
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return array.indexOf(searchElement, fromIndex);
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}
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function polyfillIndexOf(array, searchElement, fromIndex) {
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// Production steps of ECMA-262, Edition 5, 15.4.4.14
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// Reference: http://es5.github.io/#x15.4.4.14
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var k;
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// 1. Let O be the result of calling ToObject passing
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// the array value as the argument.
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if (array == null) {
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throw new TypeError('"array" is null or not defined');
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}
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var O = Object(array);
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// 2. Let lenValue be the result of calling the Get
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// internal method of O with the argument "length".
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// 3. Let len be ToUint32(lenValue).
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var len = O.length >>> 0;
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// 4. If len is 0, return -1.
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if (len === 0) {
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return -1;
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}
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// 5. If argument fromIndex was passed let n be
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// ToInteger(fromIndex); else let n be 0.
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var n = +fromIndex || 0;
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if (Math.abs(n) === Infinity) {
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n = 0;
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}
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// 6. If n >= len, return -1.
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if (n >= len) {
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return -1;
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}
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// 7. If n >= 0, then Let k be n.
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// 8. Else, n<0, Let k be len - abs(n).
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// If k is less than 0, then let k be 0.
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k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);
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// 9. 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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// This is implicit for LHS operands of the in operator
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// b. Let kPresent be the result of calling the
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// HasProperty internal method of O with argument Pk.
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// This step can be combined with c
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// c. If kPresent is true, then
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// i. Let elementK be the result of calling the Get
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// internal method of O with the argument ToString(k).
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// ii. Let same be the result of applying the
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// Strict Equality Comparison Algorithm to
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// searchElement and elementK.
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// iii. If same is true, return k.
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if (k in O && O[k] === searchElement) {
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return k;
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}
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k++;
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}
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return -1;
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};
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