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54 lines
1.7 KiB
JavaScript
54 lines
1.7 KiB
JavaScript
9 years ago
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var baseIndexOf = require('../internal/baseIndexOf'),
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binaryIndex = require('../internal/binaryIndex');
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/* Native method references for those with the same name as other `lodash` methods. */
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var nativeMax = Math.max;
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/**
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* Gets the index at which the first occurrence of `value` is found in `array`
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* using [`SameValueZero`](http://ecma-international.org/ecma-262/6.0/#sec-samevaluezero)
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* for equality comparisons. If `fromIndex` is negative, it's used as the offset
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* from the end of `array`. If `array` is sorted providing `true` for `fromIndex`
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* performs a faster binary search.
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*
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* @static
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* @memberOf _
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* @category Array
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* @param {Array} array The array to search.
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* @param {*} value The value to search for.
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* @param {boolean|number} [fromIndex=0] The index to search from or `true`
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* to perform a binary search on a sorted array.
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* @returns {number} Returns the index of the matched value, else `-1`.
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* @example
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*
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* _.indexOf([1, 2, 1, 2], 2);
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* // => 1
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*
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* // using `fromIndex`
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* _.indexOf([1, 2, 1, 2], 2, 2);
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* // => 3
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*
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* // performing a binary search
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* _.indexOf([1, 1, 2, 2], 2, true);
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* // => 2
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*/
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function indexOf(array, value, fromIndex) {
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var length = array ? array.length : 0;
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if (!length) {
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return -1;
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}
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if (typeof fromIndex == 'number') {
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fromIndex = fromIndex < 0 ? nativeMax(length + fromIndex, 0) : fromIndex;
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} else if (fromIndex) {
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var index = binaryIndex(array, value);
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if (index < length &&
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(value === value ? (value === array[index]) : (array[index] !== array[index]))) {
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return index;
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}
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return -1;
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}
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return baseIndexOf(array, value, fromIndex || 0);
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}
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module.exports = indexOf;
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