Dynamic queries in BIRT - query text replacement

var selectedParams = params["calltypes"].value;
var selectedString = "";
for (var counter=0; counter < selectedParams.length; counter++) {
 selectedString += selectedParams[counter] + ",";
}
selectedString = selectedString.substring(0,selectedString.length-1);
var before = this.queryText.toString();
var injection = "";
injection =  selectedString;
this.queryText = before.replace('53279',injection);