Slide 11.f: JavaScript variables

JavaScript Variables

You can create a variable with the var statement. Rules for variables include:

 var  strname = some value;

Variable names are case sensitive. Actually, JavaScript is case-sensitive! A variable named strname is not the same as a variable named STRNAME!

They must begin with a letter or the underscore character.

When you declare a variable within a function, the variable can only be accessed within that function. When you exit the function, the variable is destroyed. These variables are called local variables.

If you declare a variable outside a function, all the functions on your page can access it. The lifetime of these variables starts when they are declared, and ends when the page is closed.

 <html><body>
  <script type="text/javascript">
   var  bool = confirm( "Go back to the previous page?" );
   if ( bool == true ) {
    window.location = document.referrer;
   }
   else if ( bool == false ) {
    document.write ( "<a href='" + document.referrer + "'>Back</a>" );
   }
  </script>
 </body></html>

The above script returns to the current page by using a boolean variable:

The method confirm of the object window displays a confirm dialog box with the specified message and OK and Cancel buttons. It returns true if the user chooses OK and false if the user chooses Cancel.

The window's property location contains information on the current URL.

Demonstration


<html> <head> <script type="text/javascript"> </script> </head> <body> <script type="text/javascript"> </script> </body> </html>