function replaceStr(s,oldChr,newChr,NoCase){
	if(NoCase == undefined){
		s = s.split(oldChr).join(newChr);
		return s;
	}
	var newStr = s;
	var len = oldChr.length;
	oldChr = oldChr.toLowerCase();
	s = s.toLowerCase();
	var pos  =  s.indexOf(oldChr) ;
	while( pos != -1){
		newStr = newStr.substr(0,pos) + newChr + newStr.substr(pos+len);
		s = s.substr(0,pos) + newChr + s.substr(pos+len);
		pos  =  s.indexOf(oldChr) ;
	}
	return newStr;
}</p>
<p>var str = "erter www WwW rter wwW ert";</p>
<p>trace(replaceStr(str,"www","***"));</p>
<p>trace(replaceStr(str,"www","***",1));