ReferenceError: variable is not defined

javascript variables definition var
Andrew Liu picture Andrew Liu · Jul 11, 2013 · Viewed 103.2k times · Source

I met this issue sometimes but still don't know what causes it.

I have this script in the page:

$(function(){
    var value = "10";
});

But the browser says "ReferenceError: value is not defined". However if I go to the browser console and input either

10

or

var value = "10";

either of them can return 10. What is the problem with my script?

Answer

McGarnagle picture McGarnagle · Jul 11, 2013

It's declared inside a closure, which means it can only be accessed there. If you want a variable accessible globally, you can remove the var:

$(function(){
    value = "10";
});
value; // "10"

This is equivalent to writing window.value = "10";.

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