How to make a local variable into a global in JavaScript

Question

How can I make a local variable inside a function into a global in JavaScript?

P.S: Just pure JavaScript, no jQuery.

P.P.S.: Nothing toooo complicated, thanks. :)

What are you trying to achieve? Maybe there is a simpler solution. — Fábio Santos, Jan 11 '15 at 14:11
@FaridNouriNeshat Ok, tnx for finding that... I retracted my close vote... now let us close it against the correct dupe... — rene, Jan 11 '15 at 15:05
@sbedulin Please don't do that. It's *The Horror of Implicit Globals*. — Oriol, Jan 12 '15 at 16:29

score 10 · Accepted Answer · edited Nov 05 '20 at 00:18

10

You can do the following to access a global inside of a function.

Any variable created outside the scope of a function can be referenced inside of a function.

Var myGlobalVar;

Function myFunction(){
   if(....) {
        myGlobalVar = 1;
   }
}

edited Nov 05 '20 at 00:18

Peter Mortensen

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answered Jan 11 '15 at 14:03

matcartmill

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This helped in my situation. – MThead Jan 11 '15 at 14:14

score 6 · Answer 2 · answered Jan 11 '15 at 14:01

6

You don't.

You can copy a local variable to the global scope by doing window.myVar = myVar (replacing window by whatever is your global object), but if you reassign the local one, the global copy won't follow.

answered Jan 11 '15 at 14:01

Fábio Santos

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score 3 · Answer 3 · edited Nov 05 '20 at 00:21

3

You can assign a key to the window object. It'll be a global variable.

function foo(){
   var bar1; // Local variable
   bar1 = 11;
   window.bar2 = bar1; // bar2 will be global with same value.
}

Or

In pure JavaScript, if you will declare a variable without var anywhere, it will be in the global scope.

function foo(){
   var bar1; // Local variable
   bar1 = 11;
   bar2 = bar1; // bar2 will be global with same value.
}

Note: In the above text, if bar2 won't be declared yet, it will go to the window scope, otherwise it will just update bar2. If you want to make sure about using the global one, use like window.bar2 = bar1.

edited Nov 05 '20 at 00:21

Peter Mortensen

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answered Jan 11 '15 at 14:00

Mritunjay

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That's not a declaration, that's just an assignment to a non-local variable. – Bergi Jan 11 '15 at 14:05
1

@Bergi but it will be in global scope. – Mritunjay Jan 11 '15 at 14:06
1

…as long as it was not declared in a (non-global) parent scope of `foo`. – Bergi Jan 11 '15 at 14:07
1

@Bergi updated the answer, thanx, actually I was not thinking that there will be other code also. – Mritunjay Jan 11 '15 at 14:12
2

That's *The Horror of Implicit Globals*. Better avoid it. And it won't work in strict mode. – Oriol Jan 12 '15 at 16:31

How to make a local variable into a global in JavaScript

3 Answers3

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