CODEWITHSUNDEEP
javascriptvariablesscope
Vranvs
Vranvs

Reputation: 1521

JS Global and Local Variables

I have been struggling trying to get some code to work and I think its due to my variable scopes. Instead of posting all my code here, I just made a simplified version to ask "why doesn't this work":

$(document).ready(function() {

console.log("INITIALIZE");
var aGlobalVariable = 25;

function testFunction(){

    var aLocalVariable = 5;

    var sumVariables = aGlobalVariable + aLocalVariable;

    console.log(sumVariables);
}

});

I would expect the testFunction to be able to see aGlobalVariable, add 25 to 5, and output 30. it doesn't do this. I can't even see the global variable if I try to do a console.log of it:

enter image description here

Is a variable declared at the start of a document not a global one????

thanks!

Upvotes: 1

Views: 44

Answers (3)

orcaman
orcaman

Reputation: 6551

aGlobalVariable is indeed known inside testFunction. Make a call to that function and check out the console:

$(document).ready(function() {

    console.log("INITIALIZE");
    var aGlobalVariable = 25;

    function testFunction() {

        var aLocalVariable = 5;  
        var sumVariables = aGlobalVariable + aLocalVariable;

        console.log(sumVariables);
    }

    testFunction();
});

Here's a jsfiddle showing this: https://jsfiddle.net/0c8rpLmj/

aGlobalVariable is undefined when you try to view it via the console since it's not in fact global (you have defined it under the ready function scope).

Upvotes: 2

Quentin
Quentin

Reputation: 943142

Function expressions create variable scopes too.

$(document).ready(function() {
    var aGlobalVariable = 25;

Your variable is inside a function and declared with var so it isn't a global.

Move it outside the function expression if you want to make it a global.

var aGlobalVariable = 25;
$(document).ready(function() {

That said, making it a global probably isn't a good idea. Keeping it inside a local scope, but accessible to all the functions in that scope, means you have less change of other scripts interfering with your variable.

Upvotes: 0

Script47
Script47

Reputation: 14530

That isn't a global variable. Define it outside of the ready function.

var aGlobalVariable = 25;

$(document).ready(function() {

    console.log("INITIALIZE");


    function testFunction(){

        var aLocalVariable = 5;

        var sumVariables = aGlobalVariable + aLocalVariable;

        console.log(sumVariables);
   }

});

Now you should be able to see it work.

Upvotes: 0

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