How to get elements of specific class starting with a given string?

Question

I have a list of elements that have multiple classes, for example:

Answer 1

 // Only select input which have class 
 $('input[class]').click(function(){  
   var myClass;
   // classNames will contain all applied classes
   var classNames = $(this).attr('class').split(/\s+/);  

     // iterate over all class  
     $.each(classNames, function(index, item) {
        // Find class that starts with btn-
        if(item.indexOf("btn-") == 0){
          // Store it
          myClass = item;
        }
     });

  });

Live Demo