add event listener on click

let element = document.getElementById("xyz");
//	Event Listener
element.addEventListener("click",  myFunction);

// Call Function On Click
function myFunction() {
  alert("Hello World!");
} 

var element=document.getElementById("some_id");
var listener=element.addEventListener('click',function(event){                          
            
 }); 

 document.getElementById("myBtn").addEventListener("click", function(){
  document.getElementById("demo").innerHTML = "Hello World";
}); 

 document.getElementById("myBtn").addEventListener("click", function() {
  document.getElementById("demo").innerHTML = "Hello World";
}); 

 document.getElementById("myBtn").addEventListener("click", function(){
  this.style.backgroundColor = "red";
});