lodash/collection/includes.js

define(['../internal/baseIndexOf', '../lang/isArray', '../internal/isIterateeCall', '../internal/isLength', '../lang/isString', '../object/values'], function(baseIndexOf, isArray, isIterateeCall, isLength, isString, values) {

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

  /**
   * Checks if `value` is in `collection` using `SameValueZero` for equality
   * comparisons. If `fromIndex` is negative, it is used as the offset from
   * the end of `collection`.
   *
   * **Note:** [`SameValueZero`](https://people.mozilla.org/~jorendorff/es6-draft.html#sec-samevaluezero)
   * comparisons are like strict equality comparisons, e.g. `===`, except that
   * `NaN` matches `NaN`.
   *
   * @static
   * @memberOf _
   * @alias contains, include
   * @category Collection
   * @param {Array|Object|string} collection The collection to search.
   * @param {*} target The value to search for.
   * @param {number} [fromIndex=0] The index to search from.
   * @param- {Object} [guard] Enables use as a callback for functions like `_.reduce`.
   * @returns {boolean} Returns `true` if a matching element is found, else `false`.
   * @example
   *
   * _.includes([1, 2, 3], 1);
   * // => true
   *
   * _.includes([1, 2, 3], 1, 2);
   * // => false
   *
   * _.includes({ 'user': 'fred', 'age': 40 }, 'fred');
   * // => true
   *
   * _.includes('pebbles', 'eb');
   * // => true
   */
  function includes(collection, target, fromIndex, guard) {
    var length = collection ? collection.length : 0;
    if (!isLength(length)) {
      collection = values(collection);
      length = collection.length;
    }
    if (!length) {
      return false;
    }
    if (typeof fromIndex != 'number' || (guard && isIterateeCall(target, fromIndex, guard))) {
      fromIndex = 0;
    } else {
      fromIndex = fromIndex < 0 ? nativeMax(length + fromIndex, 0) : (fromIndex || 0);
    }
    return (typeof collection == 'string' || !isArray(collection) && isString(collection))
      ? (fromIndex < length && collection.indexOf(target, fromIndex) > -1)
      : (baseIndexOf(collection, target, fromIndex) > -1);
  }

  return includes;
});