what is add event listener code example

Example 1: js addeventlistener

document.getElementById("example").addEventListener('click', function() {
  alert('Click');
});

Example 2: javascript addeventlistener

var element = document.getElementById("#id");
element.addEventListener('click', function(){
	console.log("click");
});

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 */
  }
}