Well you should first learn the distinction between PHP and Javascript. The code snip you showed looks like Javascript but has variables:
}else{
li.innerHTML = '<div align="center"><table height="20" width=300><tr><td width=17><div align=right><img src=play16.png border=0></div></td><td><div align="left"><a onclick="ShowContent(\'box23\'); return true;" href="'+url+'" target="I1" ><b>'+entry.title.$t+'</div></b></a></td></tr></table></div>';
the $t appears to refer to some php variable so it would appear that you have a php script that is generating some Javascript. It's sort of hard to tell what's going on.
If you want to build an array of banned words in Javascript, it would probably look something like this:
var bannedWords = new Array('fark', 'sh!t', 'goddammit', 'george bush');
If you want a javascript function that checks a given string against that list, you'll probably need something like this:
var bannedWords = new Array('fark', 'sh!t', 'goddammit', 'george bush');
function wordIsOK(str) {
for(var i=0; i<bannedWords.length; i++) {
if (str.indexOf(bannedWords[i]) != -1) return false;
}
return true;
}