An event is a signal that something has happened.
For Example, some of the built-in events in the DOM are −
click − A pointing device button (ANY button; soon to be primary button only) has been pressed and released on an element.
mouseover − A pointing device is moved onto the element that has the listener attached or onto one of its children.
keyup − ANY key is released
load − A resource and its dependent resources have finished loading.
You can create your own events using −
You can dispatch these events on an element using dispatchEvent −
const myDiv = document.querySelector('#my-div') myDiv.dispatchEvent(new Event('my-event'));
You can add event listeners to define what to do on receiving events using addEventListener −
const myDiv = document.querySelector('#my-div') myDiv.addEventListener( // Event for which we want to listen 'my-event', // Handler Function (e) => alert('Event fired!') ); myDiv.dispatchEvent(new Event('my-event'));
Running the above code will attach an event listener to our div that will listen to my-event events. When it encounters this event it'll call the callback function.
Since we're dispatching this event, it'll be fired immediately and we'll see the alert box.