lodash/collection/includes.js

var baseIndexOf = require('../internal/baseIndexOf'),
    isArray = require('../lang/isArray'),
    isLength = require('../internal/isLength'),
    isString = require('../lang/isString'),
    values = require('../object/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` comparisons are like strict equality comparisons,
 * e.g. `===`, except that `NaN` matches `NaN`. See the
 * [ES spec](https://people.mozilla.org/~jorendorff/es6-draft.html#sec-samevaluezero)
 * for more details.
 *
 * @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.
 * @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) {
  var length = collection ? collection.length : 0;
  if (!isLength(length)) {
    collection = values(collection);
    length = collection.length;
  }
  if (!length) {
    return false;
  }
  if (typeof fromIndex == 'number') {
    fromIndex = fromIndex < 0 ? nativeMax(length + fromIndex, 0) : (fromIndex || 0);
  } else {
    fromIndex = 0;
  }
  return (typeof collection == 'string' || !isArray(collection) && isString(collection))
    ? (fromIndex < length && collection.indexOf(target, fromIndex) > -1)
    : (baseIndexOf(collection, target, fromIndex) > -1);
}

module.exports = includes;