Event Listeners (addEventListener) in javascript

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<img id="imgk" src="images/smile.jpg" width="100" height="100" border="0" />

<script>
    function smile(){
            document.getElementById('imgk').src = "images/smile.jpg";
        }
    function nosmile(){
            document.getElementById('imgk').src = "images/smile1.jpg";
        }
       
        imgk.addEventListener('mouseover',nosmile);
         imgk.addEventListener('mouseout',smile);
</script>


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