indexOf.js

var baseIndexOf = require('../internal/baseIndexOf'),
    binaryIndex = require('../internal/binaryIndex');

/* Native method references for those with the same name as other `lodash` methods. */
var nativeMax = Math.max;

/**
 * Gets the index at which the first occurrence of `value` is found in `array`
 * using [`SameValueZero`](https://people.mozilla.org/~jorendorff/es6-draft.html#sec-samevaluezero)
 * for equality comparisons. If `fromIndex` is negative, it is used as the offset
 * from the end of `array`. If `array` is sorted providing `true` for `fromIndex`
 * performs a faster binary search.
 *
 * @static
 * @memberOf _
 * @category Array
 * @param {Array} array The array to search.
 * @param {*} value The value to search for.
 * @param {boolean|number} [fromIndex=0] The index to search from or `true`
 *  to perform a binary search on a sorted array.
 * @returns {number} Returns the index of the matched value, else `-1`.
 * @example
 *
 * _.indexOf([1, 2, 1, 2], 2);
 * // => 1
 *
 * // using `fromIndex`
 * _.indexOf([1, 2, 1, 2], 2, 2);
 * // => 3
 *
 * // performing a binary search
 * _.indexOf([1, 1, 2, 2], 2, true);
 * // => 2
 */
function indexOf(array, value, fromIndex) {
  var length = array ? array.length : 0;
  if (!length) {
    return -1;
  }
  if (typeof fromIndex == 'number') {
    fromIndex = fromIndex < 0 ? nativeMax(length + fromIndex, 0) : fromIndex;
  } else if (fromIndex) {
    var index = binaryIndex(array, value),
        other = array[index];

    if (value === value ? (value === other) : (other !== other)) {
      return index;
    }
    return -1;
  }
  return baseIndexOf(array, value, fromIndex || 0);
}

module.exports = indexOf;