How can I add a event listener

Question

Please make a sample code in web

Answer 1

first grab an element from DOM
There are a few ways in which you can do that, im just gonna show you the common ways:
1) using element's id
document.getElementById("myButton")
2) using selectors that you use in css such as dot for classes and hash for ids
let myBtn = document.querySelector("#myButton")

myBtn.addEventListener("click", function(e) {
/* runs everytime you click, and i passed (e) as a paremeter which is EVENT that we automatically receive in these kind of functions */
console.log("button clicked!")
})

you could also do it like this:
myBtn.onclick = function(e) {
console.log(e.target) //shows you the whole tag on which event occurred so in this case <button id="myButton">Btn</button>
}