Could you help me? I need to know what happens in this example to not use onclick in html

Question

https://code.sololearn.com/WWCUPPTHa7bt/?ref=app

Answer 1

Use it .

window.onload=function(){
var muestra = document.querySelector(".boton");

muestra.addEventListener("click", function(){
alert("bien hecho");
});
}

Answer 2

Excellent! Thanks a lot.

Answer 3

it's better this way, right?

window.addEventListener("load", function(){
var muestra = document.querySelector(".boton");

muestra.addEventListener("click", function(){
alert("bien hecho");
});
});