Global variables in Javascript across multiple files

javascript scope global-variables global
Goro picture Goro · May 28, 2010 · Viewed 232.4k times · Source

A bunch of my JavaScript code is in an external file called helpers.js. Inside the HTML that calls this JavaScript code I find myself in need of knowing if a certain function from helpers.js has been called.

I have attempted to create a global variable by defining:

var myFunctionTag = true;

In global scope both in my HTML code and in helpers.js.

Heres what my html code looks like:

<html>
...
<script type='text/javascript' src='js/helpers.js'></script>    
...
<script>
  var myFunctionTag = false;
  ...
  //I try to use myFunctionTag here but it is always false, even though it has been se t to 'true' in helpers.js
</script>

Is what I am trying to do even feasible?

Answer

tvanfosson picture tvanfosson · May 28, 2010

You need to declare the variable before you include the helpers.js file. Simply create a script tag above the include for helpers.js and define it there.

<script type='text/javascript' > 
  var myFunctionTag = false; 
</script>
<script type='text/javascript' src='js/helpers.js'></script>     
... 
<script type='text/javascript' > 
  // rest of your code, which may depend on helpers.js
</script>

Related questions

Global javascript variable inside document.ready

Which is the right way of declaring a global javascript variable? The way I'm trying it, doesn't work $(document).ready(function() { var intro; if ($('.intro_check').is(':checked')) { intro = true; $('.intro').wrap('<div class="disabled"&…

Read More
Variables in a Javascript module visible outside of it?

To start, I'm coming from a .NET world, where there are static classes (C#, also known as modules in VB) and instance classes - those you can instantiate. This question is about Javascript, where I'm trying to recreate the pattern …

Read More
How do JavaScript closures work?

How would you explain JavaScript closures to someone with a knowledge of the concepts they consist of (for example functions, variables and the like), but does not understand closures themselves? I have seen the Scheme example given on Wikipedia, but …

Read More