how to detect form elements is changed jquery code example

Example: Determine if text is written into input text in jquery

var timerid;
$("#input").on("input", function(e) {
  var value = $(this).val();
  if ($(this).data("lastval") != value) {

    $(this).data("lastval", value);
    clearTimeout(timerid);

    timerid = setTimeout(function() {
      //your change action goes here 
      console.log(value);
    }, 500);
  };
});