Detect Whether an Event is Triggered by User and not programmatically

Question

Well this question has been asked before but in context of jQuery. In jQuery we can check it by originalEvent property of event Object (link) which tells whether its a manual or programmed event.

In my case I am using Javascript Event listeners and triggers. Can we differentiate between the two kind of events (programmed and manual) in this case?

If not then any workarounds?

My Listeners:

   function setUpListeners(){
       _cellViewWrapper.addEventListener('mousedown',mouseDownHandler,false);
       _cellViewWrapper.addEventListener('mouseover',mouseEnter,false);
       _cellViewWrapper.addEventListener('blur',blurHandler,true);
       _cellViewWrapper.addEventListener('focus',focusEventHandler,true);
   }`

Trigger use Cases:

1. if(!IE_FLAG) hidePicker();
              //if browser is internet explorer
              else{
                  //if blur is allowed then hide Picker
                  if(_ieBlurAllowed) hidePicker();
                  //if blur is not allowed -- keep focus on picker input
                 //triggering the focus event here
                  else blurredElement.focus(); /
            }
   

2. if((inputElem !== _focussedInput)) setTimeout(function(){ inputElem.focus(); },10);

and many more...

Answer 1

In latest browsers, Event.isTrusted is available for this particular use-case. As per its MDN document:

The isTrusted read-only property of the Event interface is a boolean that is true when the event was generated by a user action, and false when the event was created or modified by a script or dispatched via dispatchEvent.

You can simply check inside any event handler:

if (e.isTrusted) {
 /* The event is trusted. */
} else {
 /* The event is not trusted. */
}

Browser Support: Chrome 46.0, Firefox (latest), Opera 33, Safari & IE (no support)

Answer 2

[Workaround] Javascript: Check if event.screenX & event.screenY are non-zero.

var button = document.getElementsByTagName('button')[0];

button.onclick = function(e) {
  if(e.screenX && e.screenX != 0 && e.screenY && e.screenY != 0){
         alert("real button click");
       }   
}

When the user clicks on button, it would have some real screenX and screenY based on the button position. But when you do it from code - it would be zero