CODEWITHSUNDEEP
javascript
lelloman
lelloman

Reputation: 14183

javascript self executing functions and scoping

I read a lot of posts and ask/answer about javascript anonymous self-executing functions, but I'm afraid I'm still missing the point. Why does this code show myvar value? Shouldn't the construct (function(){ code })() keep all variables not visible from outside?

(function(){
    myvar = 5;
})();

alert(myvar);

so what's the difference betwen above code and 

function myfunction(){
    myvar = 5;
};
myfunction();

alert(myvar);

?

Upvotes: 1

Views: 165

Answers (3)

Samuele Mattiuzzo
Samuele Mattiuzzo

Reputation: 11048

Variables are scoped at the function level in javascript. What this means is if you declare a variable inside a loop or an if statement, it will be available to the entire function.

In your case, your myVar is available to the whole window as somebody pointed out already.

If you need to explicitly cage your variable inside a function scope, create an anonymous function and then execute it straight away and all the variables inside will be scoped to the function

(function(){
    var myvar = 5;
})();


alert(typeof(myVar));

results "undefined"

Upvotes: 2

asgoth
asgoth

Reputation: 35829

myvar is defined in window scope, hence it is accessible to all.

You should scope myvar IF you want to keep it private, with var:

(function(){
    var myvar = 5;
})();

Upvotes: 3

Pointy
Pointy

Reputation: 413826

You failed to declare "myvar" with var.

See what happens when you change it like this:

(function(){
    "use strict";
    myvar = 5;
})();

Upvotes: 2

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