Newbie Javascript Question

ldwdub · 26-05-2009 3:20pm #1

Newbie to Javascript so apologies.

If I have a JSP and within in it I want to use functions, for example:

<html>
   <head>
   </head>

   <body>
      <script type="text/javascript">
       int v = 64;
           int c = 8;

          document.write(v + " divided by " + c + " = " + divide(v,c));


          function divide(a,b){
             return a/b;
           }

           
     </script>
   </body>
</html>

Is this correct?

Its the functionality moreso than the exact syntax above Im looking to clarify, as I will use it in a more complex JSP.

Thanks

ron_darrell · 28-05-2009 12:13am

Ok a number of points:

That's not a JSP page - you have no java code at all there - java and javascript are two very different things
The code as written - I doubt it will work - you've defined your function after using it - that's like expecting a baby to be able to skip rope before it's learnt how to crawl
It's not a very useful piece of code even if the above issues were sorted - the values for v and c are hard-coded (that is they can't change unless you physically go in and rewrite this page) - try providing some text fields for the user to put in their values so that at least the page can be reused for numbers other than the ones you've provided

Hope that helps a bit

Regards,
RD

Giblet · 28-05-2009 8:33am

ron_darrell wrote: »

Ok a number of points:
That's not a JSP page - you have no java code at all there - java and javascript are two very different things

The code as written - I doubt it will work - you've defined your function after using it - that's like expecting a baby to be able to skip rope before it's learnt how to crawl

It's not a very useful piece of code even if the above issues were sorted - the values for v and c are hard-coded (that is they can't change unless you physically go in and rewrite this page) - try providing some text fields for the user to put in their values so that at least the page can be reused for numbers other than the ones you've provided

Hope that helps a bit

Regards,
RD

He says he has a jsp page with javascript in it. No reason to think that it isn't a jsp page, we have no idea of how that page is being rendered.

That code will work fine, it doesn't matter where the function is defined, before of after, that's how most languages work.

With regards to the code, it looks like he's testing something rather than looking to return '8' every time...

OP nothing wrong there with the syntax. Should work fine. You could prob use var instead of int.

28-05-2009 10:21am

The Hitcher wrote: »

You should use var instead of int.

This ^. Won't display without it on Firefox anyway.

mewso · 28-05-2009 10:42am

Just remember a few things about javascript.

1. Try and make your page degrade gracefully. i.e. theres something there if the user hasn't got javascript.
2. Try and put your script in an external file.
3. Whats the doctype of this page. I don't think people realise that certain javascript is not legal in xhtml strict like the document.wrtie and innerHTML function etc. Sadly as most people are serving their xhtml strict as text/html they are never made aware of this problem but when all browsers accept the correct content type of xml a lot of people out there may switch to xml and suddenly their script will stop working.

XHTML when properly served is xml and as such proper DOM manipulation is the recommended way to manipulate your content as well as pretty much the only way. So an example of how I would do this:-

<html>
   <head>
      <script type="text/javascript" src="js/myscript.js"></script>
   </head>

   <body>
      
   </body>
</html>

and in myscript.js


function initPage()   {
   var v = 64;
   var c = 8;
   var result = divide(v,c);
   var content = document.createTextNode(v + " divided by " + c + " = " + result);
   document.body.appendChild(content);
}

function divide(a,b){
   return a/b;
}

window.onload = initPage;

It should be noted I would never use a basic window.onload assignment but it serves as an example here. jQuery's $(document).ready or an alternative way of adding 1 to many load events is best.

Newbie Javascript Question

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