Global Variables - Examples

JavaScript Tutorials - Herong's Tutorial Examples

Dr. Herong Yang, Version 2.20

JavaScript Tutorials - Herong's Tutorial Examples

∟Defining and Calling Functions

∟Global Variables - Examples

This section provides a tutorial example on how global variables behave inside and outside functions.

To see how global variables behave inside and outside functions, I wrote the following tutorial example:

<html>
<!-- Global_Variable_Scope.html
   Copyright (c) 2008 by Dr. Herong Yang, http://www.herongyang.com/
-->
<head><title>Global Variable Scope</title></head>
<body>
<pre>
<script type="text/javascript">
   var globalVar;
   globalVar = "Cat";
   globalNoVar = "Dog";
  
   scopeCheck();

   document.write("\n\nAfter function call:");
   document.write("\n   globalVar = " + globalVar);
   document.write("\n   globalNoVar = " + globalNoVar);

function scopeCheck() {
   globalVar = globalVar + " - Updated";
   globalNoVar = globalNoVar + " - Updated";
   
   document.write("\n\nUpdated value in function:");
   document.write("\n   globalVar = " + globalVar);
   document.write("\n   globalNoVar = " + globalNoVar);
}
</script>
</pre>
</body>
</html>

This tutorial example tests two global variables: one declared with a "var" statement, and one without. Both variables behave identically. They are valid and accessible inside the function. See the output:

Updated value in function:
   globalVar = Cat - Updated
   globalNoVar = Dog - Updated

After function call:
   globalVar = Cat - Updated
   globalNoVar = Dog - Updated

Table of Contents

About This JavaScript Tutorial Example Book

Introduction to JavaScript

ECMAScript Language Specification and JavaScript Dialects

Data Types, Variables and Expressions

Flow Control Statements

Creating, Accessing, and Manipulating Arrays

►Defining and Calling Functions

Defining Your Own Functions

Defining Your Own Functions - Example

Calling Your Own Functions - Example

Passing Parameters by Value or by Reference