function uncamelize(str, separator) {  
      // Assume default separator is a single space.  
      if(typeof(separator) == "undefined") {  
        separator = " ";  
      }  
      // Replace all capital letters by separator followed by lowercase one  
      var str = str.replace(/[A-Z]/g, function (letter)   
      {  
        return separator + letter.toLowerCase();  
      });  
      // Remove first separator  
      return str.replace("/^" + separator + "/", '');  
    }  
    console.log(uncamelize('helloWorld'));  
    console.log(uncamelize('helloWorld','-'));  
    console.log(uncamelize('helloWorld','_'));