how does event listener work in javascript code example

Example 1: event listener javascript

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

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

Example 2: javascript event listener

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

Example 3: js add event listener

function eventHandler(event) {
  if (event.type == 'fullscreenchange') {
    /* gestire un interruttore a schermo intero */
  } else /* fullscreenerror */ {
    /* gestire un errore di commutazione a schermo intero */
  }
}