JavaScript Events

HTML events are "things" that happen to HTML elements.

When JavaScript is used in HTML pages, JavaScript can "react" on these 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 loadingAn HTML input field was changedAn 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:

<some-HTML-element some-event='some JavaScript'>

With double quotes:

<some-HTML-element some-event="some JavaScript">

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

Example

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

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In the example above, the JavaScript code changes the content of the element with id="demo".

In the next example, the code changes the content of its own element (using this.innerHTML):

Example

<button onclick="this.innerHTML = Date()">The time is?</button>

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JavaScript code is often several lines long. It is more common to see event attributes calling functions:

Example

<button onclick="displayDate()">The time is?</button>

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Common HTML Events

Here is a list of some common HTML events:

EventDescriptiononchangeAn HTML element has been changedonclickThe user clicks an HTML elementonmouseoverThe user moves the mouse over an HTML elementonmouseoutThe user moves the mouse away from an HTML elementonkeydownThe user pushes a keyboard keyonloadThe browser has finished loading the page

The list is much longer: Omegas JavaScript Reference HTML DOM Events.

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 loadsThings that should be done when the page is closedAction that should be performed when a user clicks a buttonContent that should be verified when a user inputs dataAnd more ...

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

HTML event attributes can execute JavaScript code directlyHTML event attributes can call JavaScript functionsYou can assign your own event handler functions to HTML elementsYou can prevent events from being sent or being handledAnd more ...

You will learn a lot more about events and event handlers in the HTML DOM chapters.

Test Yourself with Exercises!

Exercise 1 »   Exercise 2 »   Exercise 3 »

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