CODEWITHSUNDEEP
javascript
wukong
wukong

Reputation: 2597

why is class a reserved word in JavaScript?

I am planning to implement class inherit interface using JavaScript. class is the perfect word as the name of the constructor.

class = function (classname) {}; // create a class with classname
classA = new class("classA"); // create a class named classA

Unfortunately, class is a reserved word in JavaScript.

Why does JavaScript reserve the word class (since it never uses it)?

Upvotes: 27

Views: 15239

Answers (5)

username.ak
username.ak

Reputation: 182

Now it's used in ECMAScript® 2015 Language Specification:

class Foo {
    constructor(bar) {
        this.bar = bar;
    }
}
new Foo(10).bar; // 10

Upvotes: 7

zzzzBov
zzzzBov

Reputation: 179226

It's reserved to future-proof ECMAScript

The following words are used as keywords in proposed extensions and are therefore reserved to allow for the possibility of future adoption of those extensions.

Don't fret though, if you're using best-practices in your JavaScripts, you're placing all accessible functions/variables/constructors in a namespace, which will allow you to use whatever name you'd like:

foo = {};
foo['class'] = function(){...code...};
var myClass = new foo['class']();

Upvotes: 28

Sivakumar
Sivakumar

Reputation: 890

It is there so that support can be added in future without breaking existing programs. Please take a look at the following post.

You can also look at

https://developer.mozilla.org/en/JavaScript/Reference/Reserved_Words

Upvotes: 2

Thilo
Thilo

Reputation: 262794

Languages evolve. It is prudent to reserve a few keywords that might come in use later. According to the ECMA standard, class is a Future Reserved Word.

If you did not reserve them, introducing new keywords could conflict with existing code (which already might be using the word for other things). Happened with Java and assert.

Upvotes: 9

MikeM
MikeM

Reputation: 27415

class is reserved as a future keyword by the ECMAScript specification

Reserved Words - MDN

Upvotes: 4

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