core-js/internals/array-includes.js

'use strict';
var toIndexedObject = require('../internals/to-indexed-object');
var toAbsoluteIndex = require('../internals/to-absolute-index');
var lengthOfArrayLike = require('../internals/length-of-array-like');

// `Array.prototype.{ indexOf, includes }` methods implementation
var createMethod = function (IS_INCLUDES) {
  return function ($this, el, fromIndex) {
    var O = toIndexedObject($this);
    var length = lengthOfArrayLike(O);
    if (length === 0) return !IS_INCLUDES && -1;
    var index = toAbsoluteIndex(fromIndex, length);
    var value;
    // Array#includes uses SameValueZero equality algorithm
    // eslint-disable-next-line no-self-compare -- NaN check
    if (IS_INCLUDES && el !== el) while (length > index) {
      value = O[index++];
      // eslint-disable-next-line no-self-compare -- NaN check
      if (value !== value) return true;
    // Array#indexOf ignores holes, Array#includes - not
    } else for (;length > index; index++) {
      if ((IS_INCLUDES || index in O) && O[index] === el) return IS_INCLUDES || index || 0;
    } return !IS_INCLUDES && -1;
  };
};

module.exports = {
  // `Array.prototype.includes` method
  // https://tc39.es/ecma262/#sec-array.prototype.includes
  includes: createMethod(true),
  // `Array.prototype.indexOf` method
  // https://tc39.es/ecma262/#sec-array.prototype.indexof
  indexOf: createMethod(false)
};