@ndhoule/includes/index.js

Determine whether or not a value is contained by a given collection.

'use strict';

/*
 * Module dependencies.
 */

var each = require('@ndhoule/each');

var strIndexOf = String.prototype.indexOf;

/**
 * Object.is/sameValueZero polyfill.
 *
 * @api private
 * @param {*} value1
 * @param {*} value2
 * @return {boolean}
 */
// TODO: Move to library
var sameValueZero = function sameValueZero(value1, value2) {
  // Normal values and check for 0 / -0
  if (value1 === value2) {
    return value1 !== 0 || 1 / value1 === 1 / value2;
  }
  // NaN
  return value1 !== value1 && value2 !== value2;
};

/**
 * Searches a given `collection` for a value, returning true if the collection
 * contains the value and false otherwise. Can search strings, arrays, and
 * objects.
 *
 * @name includes
 * @api public
 * @param {*} searchElement The element to search for.
 * @param {Object|Array|string} collection The collection to search.
 * @return {boolean}
 * @example
 * includes(2, [1, 2, 3]);
 * //=> true
 *
 * includes(4, [1, 2, 3]);
 * //=> false
 *
 * includes(2, { a: 1, b: 2, c: 3 });
 * //=> true
 *
 * includes('a', { a: 1, b: 2, c: 3 });
 * //=> false
 *
 * includes('abc', 'xyzabc opq');
 * //=> true
 *
 * includes('nope', 'xyzabc opq');
 * //=> false
 */
var includes = function includes(searchElement, collection) {
  var found = false;

  // Delegate to String.prototype.indexOf when `collection` is a string
  if (typeof collection === 'string') {
    return strIndexOf.call(collection, searchElement) !== -1;
  }

  // Iterate through enumerable/own array elements and object properties.
  each(function(value) {
    if (sameValueZero(value, searchElement)) {
      found = true;
      // Exit iteration early when found
      return false;
    }
  }, collection);

  return found;
};

/*
 * Exports.
 */

module.exports = includes;