function str_replace(Search, Replace, Subject){

 if ((Subject == null) || (Search == null)) return null;
 if ((Subject.length == 0) || (Search.length == 0)) return Subject;
 if ((Replace == null) || (Replace.length == 0)) Replace = "";

 var LengthSearch = Search.length;
 var LengthReplace = Replace.length;
 var Pos = Subject.indexOf(Search, 0);

 while (Pos >= 0){
   Subject = Subject.substring(0, Pos) + Replace + Subject.substring(Pos + LengthSearch);
   Pos = Subject.indexOf(Search, Pos + LengthReplace);
 }
 
 return Subject;
}

function strstr(Haystack, Needle){

 if ((Haystack == null) || (Needle == null)) return null;
 if ((Haystack.length == 0) || (Needle.length == 0)) return null;

 var result = Haystack.indexOf(Needle);
 
 if(result<0) return false;

 return true;
}