Using 'window' with a local variable for global access in JavaScript

Question

I'd like to access a local variable globally (without changing the namespace or location of the variable). I read that I could use 'window.', but it's not working:

var myNameSpace = {
        window.localVar : 'foo'
    };

alert(window.localVar);  // Not working

JSFiddle

Can something like this work?

Also, I've read about the risks of global variables. If I'm nearly certain a variable's name isn't at risk to be reused, is it safe?

$myTotallyUniqueVarName

"but it's not working:" ... well, using window.lovalVar is syntax error at this position: but it's not working: SyntaxError: Unexpected token .`. — Felix Kling
– Felix Kling, Commented Feb 21, 2013 at 15:04

jAndy · Accepted Answer · 2013-02-21 14:31:13Z

4

var myNameSpace = { };

myNameSpace.localVar = window.localVar = 'foo';

You can't access another object when defining the key from another object, like you tried. But you certainly can create multiple references/assignments to the same value, like shown above.

However, be aware that we assigning a primitive value in this case, that means, window.localVar and myNameSpace.localVar will hold their own unique value. Any change will not reflect on the other side.

answered Feb 21, 2013 at 14:31

jAndy

237k57 gold badges313 silver badges363 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Peter Mortensen · Accepted Answer · 2020-10-15 18:47:37Z

1

Every variable that is somehow related to the global object can be accessed globally. In browsers, the window variable represents the global object.

function a() {
  bvar = 3; // Accessible
  var cvar = 4; // Inaccessible
}

a();

alert(window.bvar === 3); // true
alert(window.cvar === 4); // false, cvar is undefined

// This refers here to the global object
alert(window.bvar === this.bvar); // true

edited Oct 15, 2020 at 18:47

Peter Mortensen

31.4k22 gold badges110 silver badges134 bronze badges

answered Feb 21, 2013 at 14:38

Andries

1,52711 silver badges29 bronze badges

4 Comments

nathanbweb Over a year ago

thanks, that's helpful. so bvar is accessible because it's a key, or because it isn't a variable?

Andries Over a year ago

In JavaScript everything can be seen as an array. So, a function is an array with properties, and the global object can be seen as a array to. The function a() and bvar are both 'items' / properties on the global object. (every variable declared without the var prefix will leak into the global object.) so, window.a and window.bvar are accessable. cvar is declared inside a function and becomes a property of the functions' activation object'. Properties of activation object of functions are not accessable outside the function scope. Hope this helps, space is little here to explain this.

Felix Kling Over a year ago

@Andries: I'd rather say everything is an object. Arrays are special types of objects.

Andries Over a year ago

@Felix: True, thats why i carefully expressed myself by saying 'can be seen as'. I wanted to stress the array-behavior of JavaScript like: window['cvar'] === window.cvar. But you also right. Maybe we should say, everything is an special type of an object.:)

Collectives™ on Stack Overflow

Using 'window' with a local variable for global access in JavaScript

2 Answers 2

Comments

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related