Performance issues with javascript

I have few questions regarding performance issues with javascript:

if a jsp code contains lots of javascript methods which are not in use is that a performance issue?

what is better in terms of performance writing code in .js file and loading the file or writing code in the .jsp file itself.

what is heavy in terms of performance a div or a table or a p tag.

what other areas can/should be considered for javascript performance tuning

Putting the js into a seperate file is normally better since it gets cached.

You probably would want to look into this: http://dean.edwards.name/packer/

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Tables render slower than divs/spans. Plenty on information out there with the a google search.

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Some performance tips

http://blogs.msdn.com/ie/archive/2006/08/28/728654.aspx

Eric

if a jsp code contains lots of javascript methods which are not in use is that a performance issue?

There is a tiny performance hit, but in all likelihood it's much too small to be worth contemplating.

what is better in terms of performance writing code in .js file and loading the file or writing code in the .jsp file itself.

If you have it as part of the page it gets generated and sent every time the page is accessed. On the other hand, if you keep it in a separate file you save that effort on the server, because the browser will cache it as long as it's unchanged - much better.
[ February 05, 2008: Message edited by: Ulf Dittmer ]

I appreciate your suggestion,

But a question to eric, you have provided a link to Dean Edwards Packer;

What this does primarly is it removes whitespaces and change the names of variables to a smaller/shorter name does this helps performance ... ?

It shrinks the js file size which means it is a quicker download.

Eric