A grails var can be accessed in javascript using $ notation
var rsData = '${ruleSetData}';
If you want to convert it to JSON use encodeAsJSON()
var objJSONData = '${gObject.encodeAsJSON()}'
and parse this object in javascript using var parsedJSONData = eval(objJSONData);This obj can then be used in JS as
for(var i=0; i< parsedJSONData.length; i++){
alert(parsedJSONData[i].propertyName);
}