Best way to check for an empty string in JavaScript

For checking if a string is empty, null or undefined use:

function isEmpty(str){
   return (!str || 0===str.length);
}

For checking if a string is blank (with no tabs and spaces):

if(str.replace(/\s/g,"") == ""){
}

Tip: Grails variable in javascript

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);
}