You can do this all in one long line
code:
[...]
string = string.replace(/hello/gi,"sup").replace(/hi/gi,"yo").replace(/whatever/gi,"w/e").replace(/hey/gi,"hay");
[...]
You can do these all individually and you can set the regular expressions as variables like I did before, but why bother if you only have a small list like this. Unfortunately I don't think it is possible to use a for count and an array so you will have to keep changing the script itself (though if anyone can prove me wrong I will be appreciative).