Shoutbox

Hey guys, im having trouble with javascript coding. I know for a fact that this comunity has a lot of genus coders which is why im asking here first.

Anyways, what i wanna acomplish is:

I've got a div tag with a content "hello world"
ie: <div>hello world</div>

Now what I wanna do is take out anything after 4 letters in that div tag
ie: so im left with the word 'hell' in the end. instead of 'hello world'

I know i can use:
x=x.substr(0,4);

to subtract anything after the 4rth letter but my question is... how do I apply this logic to what I wanna get acomplished?

could someone who knows what they're doing please complete the code for me so i can understand how its done right? Thanks everyone!

I've got a joost + pownce invite for the first person with the working script