Question

$('input[type="radio"]').change(function() {
  alert(this.value); 
});

this.value here already contains new value. How can I get previous value (i.e. prior to change value)?

Answer 1

Since there is no such event, I had to store prev value in data-original-value attribute:

$('input[type="radio"]').change(function() {          
  alert(this.name + ': ' + $(this).parents("div.control-group").attr('data-original-value') + ' -> ' + this.value);
  $(this).parents("div.control-group").attr('data-original-value', this.value);
});