Pfthb

I'm trying to polyfill the array method includes() to work with IE8, which I need to support for a project and I don't want to use indexOf().

I know there's a polyfill, so I went to:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes#Polyfill

And included it at the top of my script.

IE8 has limited support for Object.defineProperty() so I polyfilled it as well:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperties#Polyfill

Lastly, I needed to polyfill Object.keys():
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys#Polyfill

Put together, my polyfills are:

if (!Object.keys) 
 Object.keys = (function() 
 'use strict';
 var hasOwnProperty = Object.prototype.hasOwnProperty,
 hasDontEnumBug = !( toString: null ).propertyIsEnumerable('toString'),
 dontEnums = [
 'toString',
 'toLocaleString',
 'valueOf',
 'hasOwnProperty',
 'isPrototypeOf',
 'propertyIsEnumerable',
 'constructor'
 ],
 dontEnumsLength = dontEnums.length;

 return function(obj) 
 if (typeof obj !== 'function' && (typeof obj !== 'object' ;
 ());


function defineProperties(obj, properties) 
 function convertToDescriptor(desc) desc === null)
 throw new TypeError('bad desc');

 var d = ;

 if (hasProperty(desc, 'enumerable'))
 d.enumerable = !!desc.enumerable;
 if (hasProperty(desc, 'configurable'))
 d.configurable = !!desc.configurable;
 if (hasProperty(desc, 'value'))
 d.value = desc.value;
 if (hasProperty(desc, 'writable'))
 d.writable = !!desc.writable;
 if (hasProperty(desc, 'get')) 
 var g = desc.get;

 if (!isCallable(g) && typeof g !== 'undefined')
 throw new TypeError('bad get');
 d.get = g;
 
 if (hasProperty(desc, 'set')) 
 var s = desc.set;
 if (!isCallable(s) && typeof s !== 'undefined')
 throw new TypeError('bad set');
 d.set = s;
 

 if (('get' in d 

 if (typeof obj !== 'object' 

if (!Array.prototype.includes) 
alert('test');

 defineProperties(Array.prototype, 'includes', 
 value: function(searchElement, fromIndex) 0;

 // 5. If n ≥ 0, then
 // a. Let k be n.
 // 6. Else n < 0,
 // a. Let k be len + n.
 // b. If k < 0, let k be 0.
 var k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);

 function sameValueZero(x, y) 
 return x === y 

 // 7. Repeat, while k < len
 while (k < len) 
 // a. Let elementK be the result of ? Get(O, ! ToString(k)).
 // b. If SameValueZero(searchElement, elementK) is true, return true.
 if (sameValueZero(o[k], searchElement)) 
 return true;
 
 // c. Increase k by 1. 
 k++;
 

 // 8. Return false
 return false;
 
 );

To test the above script, I did:

var arr = ["one", "two", "three"];

alert( arr.includes('two') );

IE8 throws this error:

Object doesn't support this property or method.

I thought that by using polyfills, I would be able to add support for array includes() to IE8. What am I doing wrong? Any corrections or links to other polyfills are welcomed. No jQuery or other libraries. I just want to add support for includes() to IE.

use arr.indexOf('two')

if return 1 is because it exists, and -1 does not exist

Unfortunately I don't have a way to test in IE8, but I think there are a couple of things going on here -- first, you don't need to define defineProperties(obj, properties) because neither the Object.keys nor Array.prototype.includes polyfills use it -- they are both self-contained. The fact that they are self-contained also means that you don't need to include the Object.keys polyfill.

I would suggest only using the includes Array.prototype.includes if that is all you need.

You can simply use Array#indexOf to polyfill Array#includes.

For IE8, you will also need to polyfill Array#indexOf as it was only implemented in IE9.

if(!Array.prototype.includes)
 //or use Object.defineProperty
 Array.prototype.includes = function(search)
 return !!~this.indexOf(search);
 

if(!Array.prototype.indexOf)
Array.prototype.indexOf = (function(Object, max, min)
 "use strict";
 return function indexOf(member, fromIndex) this===undefined)throw TypeError("Array.prototype.indexOf called on null or undefined");

 var that = Object(this), Len = that.length >>> 0, i = min(fromIndex ;
)(Object, Math.max, Math.min);

Array.prototype.includes = null;
Array.prototype.indexOf = null;
if(!Array.prototype.includes)
 console.log('Polyfilled Array.prototype.includes');
 //or use Object.defineProperty
 Array.prototype.includes = function(search)
 return !!~this.indexOf(search);
 

if(!Array.prototype.indexOf)
 console.log("Polyfilled Array.prototype.indexOf");
Array.prototype.indexOf = (function(Object, max, min)
 "use strict";
 return function indexOf(member, fromIndex) 
 if(this===null;
)(Object, Math.max, Math.min);

var obj = x: 1, y: 2;
var arr = [1, 'what', obj];
console.log('Array includes 1:',arr.includes(1));
console.log('Array includes 'what':', arr.includes('what'));
console.log('Array includes obj:', arr.includes(obj));
console.log('Array inclues 3:', arr.includes(3));