Solved

How do I override a base class method in Javascript

Posted on 2008-06-24
7
561 Views
Last Modified: 2012-08-14
I have a base class defined as follows
BaseClass = function(id)
{
this.ID = document.getElementById(id);
this.Show() = function() {
document.getElementById(this.ID).style.display = 'block';
};
}
and an inherited class defined as follows

Label = function(id)
{
this.inheritFrom = BaseClass;
this.inheritFrom(id);
}
I want to introduce a Show method on the Label class so that it overrides the base class method, calls the base class method and adds it's own extra implementation for this method.  How can I do this?
Thanks
0
Comment
Question by:kayhustle
  • 4
  • 2
7 Comments
 
LVL 142

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 21863911
use the "super" "object" to call the inherited classes method.
0
 
LVL 1

Author Comment

by:kayhustle
ID: 21865115
How do I do that?
0
 
LVL 142

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 21865215
this should explain it all:
http://phrogz.net/JS/Classes/OOPinJS2.html
0
Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

 
LVL 1

Author Comment

by:kayhustle
ID: 21867323
Can you give me a code example, not sure I follow your link.
0
 
LVL 1

Author Comment

by:kayhustle
ID: 21867764
Yeah I tried about 4 different variations of what was given in the article and none of them worked.
0
 
LVL 16

Accepted Solution

by:
Lolly-Ink earned 500 total points
ID: 21870721
Here is a working example based on your original code. There were some errors in BaseClass which have been fixed:
<html>

<script>

   BaseClass = function(id)

   {

      this.id = id;

      this.Show = function()

      { 

         document.getElementById(this.id).style.display = 'block';

      }

   }
 

   Label = function(id)

   {

      this.inheritFrom = BaseClass;

      this.inheritFrom(id);

      this._Show = this.Show;

      this.Show = function()

      {

         this._Show();

         document.getElementById(this.id).style.backgroundColor = 'red';

      }

   }
 

   var one = new BaseClass("spanOne");

   var two = new Label("spanTwo");
 

   function load()

   {

      window.setTimeout("changeSpans()", 2000);

   }
 

   function changeSpans()

   {

      one.Show();

      two.Show();

   }

</script>

<body onload="load()">

   <span id="spanOne">One</span>

   <span id="spanTwo">Two</span>

</body>

</html>

Open in new window

0
 
LVL 1

Author Closing Comment

by:kayhustle
ID: 31470352
Perfect!
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Having worked on larger scale sites, we found out that you are bound to look at more scalable solutions to integrating widgets, code snippets or complete applications and mesh them into functional sites, in any given composition. To share some of…
Introduction A frequently asked question goes something like this:  "I am running a long process in the background and I want to alert my client when the process finishes.  How can I send a message to the browser?"  Unfortunately, the short answer …
The viewer will learn the basics of jQuery, including how to invoke it on a web page. Reference your jQuery libraries: (CODE) Include your new external js/jQuery file: (CODE) Write your first lines of code to setup your site for jQuery.: (CODE)
The viewer will learn the basics of jQuery including how to code hide show and toggles. Reference your jQuery libraries: (CODE) Include your new external js/jQuery file: (CODE) Write your first lines of code to setup your site for jQuery…

911 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

21 Experts available now in Live!

Get 1:1 Help Now