var classname = document.getElementsByClassName("classname");
var myFunction = function() {
var attribute = this.getAttribute("data-myattribute");
alert(attribute);
};
for (var i = 0; i < classname.length; i++) {
classname[i].addEventListener('click', myFunction, false);
}
let element = document.getElementById("xyz");
// Event Listener
element.addEventListener("click", myFunction);
// Call Function On Click
function myFunction() {
alert("Hello World!");
}