Events
An event may occur when
- The user selects, clicks, or hovers the cursor over a certain element.
- The user chooses a key on the keyboard.
- The user resizes or closes the browser window.
- A web page finishes loading.
- A form is submitted.
- A video is played, paused, or finishes.
- An error occurs.
Events Handler
To react to an event, you attach an event handler to it. This is a block of code (usually a JavaScript function that you as a programmer create) that runs when the event fires. When such a block of code is defined to run in response to an event, we say we are registering an event handler.
Web events are not part of the core JavaScript language — they are defined as part of the APIs built into the browser.
onload
Execute a JavaScript immediately after a page has been loaded: