//standard event
document.querySelector(".target").addEventListener("click",function(){
print("standard event handler");
});
//delegate event handler
document.querySelector("#parent").addEventListener("click",function(e){
if (e.target===document.querySelector(".target"))//check if we clicked on .target
print("delegate event handler");
});
<div id="parent"> ===================== <button class="target"> Click me! </button> ===================== </div>