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Variables In Javascript

In this article, we will discuss variables in JavaScript.

What Is A Variable?

Variables are the containers for storing information.

How To Declare A Variable?

In JavaScript, variables are declared using the var keyword.

var author_name;

Example

<html>
   <head>
      <title>Variable example</title>
      <script language="JavaScript">	
         function ClickMe()
         {
             var alert_text = "Hi, this is the variable tutorial";
              alert(alert_text);
         }				
      </script>
   </head>
   <body>
      <form>
         <input type="button" name="btnComments" value="Click Me" onclick="javascript:ClickMe();">
      </form>
   </body>
</html>

Try It

In the above code, the alert_text is a variable for storing string data.

Rules Of Creating A Variable

Variable name should not be a keyword
Variable names should always start with an alphabet or underscore (_)
Variable names are case-sensitive

Global And Local Variable

A local variable is visible within the function where it is defined. Whereas a global variable is visible throughout the page.

Consider the following example: -

var global_variable = "This is the global variable";

function ClickMe() {
    var local_variable = "This is the local variable";
    alert(local_variable);
    ClickMeAgain();
}

function ClickMeAgain() {
    alert(global_variable);
}

In the above example, global_variable can be accessed in the ClickMe and ClickMeAgain functions whereas the local_variable is local to the ClickMe function.

Posted By -	Karan Gupta

Posted On -	Wednesday, December 1, 2010

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