Behavior of removeEventListener

You have to specify the exact function you've specified to addEventListener as the second argument. If you specified the third useCapture argument, you'll have to specify the same and equivalent to removeEventListener as well.

For example:

function myFunc(event){ alert(event.target.textContent); }

var myElement=document.getElementById('myElement');

//Add EventListener
myElement.addEventListener('click', myFunc, false );

/* ... */

//Remove EventListener
myElement.removeEventListener('click', myFunc, false );

↪ View an example at jsFiddle

You can find more information at the Mozilla Developer wiki.

removeEventListener takes 2 parameters, the event, and the function to remove.
This should work:

document.getElementById("div1").removeEventListener("click", clickfn);

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Also, the function you're executing is empty.

var clickfn = function(){  };