Persistent JavaScript Execution

Hi,

I’m pretty new to wordpress and just trying to find out what can be done with it and how. So currently I’d like to do a little background animation with a little javascript. The script itself works fine but unfortunatly it get’s restartet each time something is pressed because the page is reloaded. I want the script to be loaded just once and then to continuous run until the page is open. So the question is, is there any way to start a script once the page has finished loading ?

thanks for your help!
Thorsten