JavaScript Events

HTML Events

An HTML event can be something the browser does, or something a user does.

Here are some examples of HTML events:

• An HTML web page has finished loading
• An HTML input field was changed
• An HTML button was clicked

Often, when events happen, you may want to do something.

JavaScript lets you execute code when events are detected.

HTML allows event handler attributes, with JavaScript code, to be added to HTML elements.

With single quotes:

<element event='some JavaScript'>

With double quotes:

<element event="some JavaScript">

In the following example, an onclick attribute (with code), is added to a button element:

<button onclick="document.getElementById('demo').innerHTML = Date()">The time is?</button>

Common HTML Events

Here is a list of some common HTML events:

Event                         Description
onchange                   An HTML element has been changed
onclick                      he user clicks an HTML element
onmouseover            The user moves the mouse over an HTML element
onmouseout             The user moves the mouse away from an HTML element
onkeydown              The user pushes a keyboard key
onload                      The browser has finished loading the page

What can JavaScript Do?

Event handlers can be used to handle, and verify, user input, user actions, and browser actions:

• Things that should be done every time a page loads
• Things that should be done when the page is closed
• Action that should be performed when a user clicks a button
• Content that should be verified when a user inputs data
• And more ...

Many different methods can be used to let JavaScript work with events:

• HTML event attributes can execute JavaScript code directly
• HTML event attributes can call JavaScript functions
• You can assign your own event handler functions to HTML elements
• You can prevent events from being sent or being handled
• And more ...