Google Tag Manger Custom Events

util-gtm-onchange.js

<script>

   var selectEls = document.getElementsByTagName('select'),
       selectIdx = selectEls.length,
       customEvent = {};

   function addListener( element, type, callback ) {
      if ( element.addEventListener ) element.addEventListener( type, callback );
      else if ( element.attachEvent ) element.attachEvent( 'on' + type, callback );
   }

   while ( --selectIdx >= 0 ) {
      addListener( selectEls[selectIdx], 'change', function() {
         customEvent = {
             "event": "gtm.change",
             "gtm.element": this,
             "gtm.elementClasses": this.className,
             "gtm.elementId": this.id,
             "gtm.elementTarget": this.target 
         };
         dataLayer.push(customEvent);
      });
   }

</script>

util-gtm-onkeydown.js

<script>
  var ENTER_KEY = 13;
  var els, elsIdx, customEvent = {};

  function addListener( element, type, callback ) {
    if ( element.addEventListener ) element.addEventListener( type, callback );
    else if ( element.attachEvent ) element.attachEvent( 'on' + type, callback );
  }

  function findAllInputsElements() {
    return document.getElementsByTagName('input');
  }

  els = findAllInputElements();
  elsIdx = els.length;
  
  while ( --elsIdx >= 0 ) {
    addListener( els[elsIdx], 'keydown', function(e) {
      var evt = e || window.event,
            key = evt.which ? evt.which : evt.keyCode;

      if( key !== ENTER_KEY ) { return; }

      customEvent = {
        "event": "gtm.keydown",
        "gtm.element": this,
        "gtm.elementClasses": this.className,
        "gtm.elementId": this.id,
        "gtm.elementTarget": this.target 
      };

      dataLayer.push(customEvent);
    });
  }

</script>