add event listener to button code example

Example 1: javascript onclick event listener

document.getElementById("myBtn").addEventListener("click", function() {
  alert("Hello World!");
});

Example 2: event listener javascript

const element = document.querySelector(".class__name");

element.addEventListener("click", () => {
	console.log("clicked element");
});

Example 3: javascript pass parameter to event listener

var someEventHander=function(){
	console.log(event,param1,param2);
}
//add listener
document.getElementById("someid").addEventListener('click',someEventHander.bind(event,param1,param2));

Example 4: javascript event listener

element.addEventListener("click", function(){ 
   element.innerText = "something"; 
});

Example 5: how to add event listener to all buttons

<button class="btn">
    Button1
</button>
<button class="btn">
    Button2
</button>
<button class="btn">
    Button3
</button>
<button class="btn">
    Button4
</button> //HTML

//JavaScript
var buttons = document.querySelectorAll(".btn").length;

for (var i = 0; i < buttons ; i++) {
    document.querySelectorAll(".btn")[i].addEventListener("click", function() {
        alert("Button Clicked");
    });
}