Admin Forum:Some curiosities about Javascript

I always ask myself next questions, if somebody can answer one of them, please reply me.
 * 1) Unless there's no conflict between scrpits, can I put as much script as I want? (I mean by much, 3~5 times as much than most of wikia sites, for example.)
 * 2) Some scripts that I'm using is destinated to affect only elements on the main page. Are these scripts loaded on every article load? I'm afraid they make the site slow or so.
 * 3) Does the following two codes do same thing on wikia sites?