Note : The VALUE tag for the checkboxes seem to have no use. But it is required to differentiate between the check boxes when you submit such a form to a server side program. You could differentiate between the checked boxed by giving different VALUEs to the checkbox.
When you press submit on this script it first sets the variable totalboxes = 2, then it also sets the target for the form using the 3 if conditions stated. Then it calls the isReady() function and checks to see if atleast one checkbox has been checked. If even one is checked then it returns true and this causes the contents to be submitted to either program1.jsp or program2.jsp or program3.jsp. If even one checkbox wasn't checked you would be notified with a alert dialog box.
The setCount() take 2 parameters, the no of checkboxes and the target program to which the contents have to be submitted to.
Note : Sending the variable 5 for no of boxes using the onClick() event is useful in case you are not knowing the no. of checkboxes while writing the top part of the html page (while writing the script part at the top of the page). This may happen in case you are dynamically creating this html page then you may not know how many checkboxes would be present in the beginning. Basically this thing becomes useful since the dynamic languages such as ASP or JSP would generate the page line by line and at that time you would first generate the script part and then the actual checkboxes on the page. So you would not be able to set the value of totalboxes to a finite number before actually adding all the checkboxes to the page. You could use a counter (within ASP/JSP) which keeps track of the checkboxes you add to the html page and finally set the value of that counter as a parameter to this onClick() function.
Example 4 : Emulating Browsers Back-Forward buttons
This is a simple script that many programmers know. Most of the users feel that this is a waste since the browsers Forward-Back buttons are already present. But you would realize that in case you are creating a window without the standard toolbars as shown in Example No.3 , then you would find this script to be very useful to emulate the Browsers buttons.
I have shown 2 ways.. I prefer the image one, since it looks really neat in case you have nice image.
Below is the source of leftindex.html
You require 5 images named countdown1.jpg, countdown2.jpg ..so on till countdown5.jpg each with repective digits on them, in the same directory as the script. When you load this page, after a delay of 2 seconds the images are displayed in the reverse order (from 5 down to 1) each after a delay of 1 second. This gives it a kewl effect of a countdown from 5 to 1 and then when it finishes a new blank window opens. The opening of a blank window was the simplest thing to use here. You can replace that with any other command.
I had used a slightly modified version of this countdown script during a press release of one of the websites I had developed. After the countdown the website opened in the new window. Ofcourse it was accompanied with claps and wows from the crowd present there :-) The effects looked wonderful since I had used 5 animated gifs, with each of them showing a sort of transformation (morphing) from one digit to another.
Alternatively in case you want to change an image when clicked on it use the following script
In the above script when the user selects either Cricket or Tennis in the first Select Menu, the choices in the second Select Menu automatically changes accordingly.