Automating interaction with a web-page's JavaScript

Some websites, like rapidshare, give access to their content using JavaScript-based timers.

This is impossible to circumvent, for someone like me who doesn't really know how web browsers exactly work.

I'd be grateful if someone could provide me with a helpful article explaining how to handle this obstacle (scripts and cookies).

Editor's note: The title was "Automating server-side javascript", which is not technically correct based on the rest of the questio开发者_JS百科n. But I'm leaving the old title text here, in case other users search with the same notions in mind.

You want to change the way a web-site acts when you browse it, yes?

For this, use browser-scripting tools like Greasemonkey¹.

Userscripts.org has a collection of scripts that work for a variety of sites -- including scripts for, say, Rapidshare.

Find a script that does what you want, or tweak a script that's close.
You can sometimes talk people on the Userscripts.org forum into writing new scripts, and SO (here) can help with specific script programming questions.

¹ Greasemonkey is mainly for Firefox, but works to various degrees on Chrome, Opera, Safari, and even IE (very limited).   GM scripts work fairly well on Chrome -- especially when using the Tampermonkey extension.

Javascript is a client-side technology. For server-side, you need something like JSP, ASP, or PHP. These require a web server to host the pages, which process the results and display the generated output to the browser.