when some process starts,stops ,its state may change or user interact with the program. In simple words an event in the books of computer programming can be defined as Event is an action or occurrence detected by a program. Events can be user actions, such as clicking a mouse button or pressing a key, or system occurrences, such as running out of memory. Most modern applications, particularly those that run in Macintosh and Windows environments, are said to be event-driven,because they are designed to respond to events.
As a webpage is made up of HTML. Therefore HTML events are the
things or actions which take place on HTML elements.
Following are the few examples which demonstrates the Events in HTML page.
When user clicks on button on webpage
when user hovers over a button on Webpage
When user clicks on Link on Webpage
When user hovers over a picture on Webpage
When a webpage complete loading.
Web developers manipulates these events to provide some functionaility through JavaScript code in webpages.
JavaScript lets you execute code when events are detected. HTML allows event handler attributes, with JavaScript code, to be added to HTML elements.
An Event can be added simply like below
<element event="some JavaScript">
For example consider the below code which uses onclick event.
<html>
<head>
<script type = "text/javascript">
<!--
function sayHello() {
alert("Hello World")
}
//-->
</script>
</head>
<body>
<p>Click the following button and see result</p>
<form>
<input type = "button" onclick = "sayHello()" value = "Say Hello" />
</form>
</body>
</html>
Click the following button and see result
Similary see what happens when user clicks on it.
The standard HTML 5 events are listed here for your reference. Here script indicates a Javascript function to be executed against that event.
| Attribute | Value | Description |
|---|---|---|
| Offline | script | Triggers when the document goes offline |
| Onabort | script | Triggers on an abort event |
| onafterprint | script | Triggers after the document is printed |
| onbeforeonload | script | Triggers before the document loads |
| onbeforeprint | script | Triggers before the document is printed |
| onblur | script | Triggers when the window loses focus |
| oncanplay | script | Triggers when media can start play, but might has to stop for buffering |
| oncanplaythrough | script | Triggers when media can be played to the end, without stopping for buffering |
| onchange | script | Triggers when an element changes |
| onclick | script | Triggers on a mouse click |
| oncontextmenu | script | Triggers when a context menu is triggered |
| ondblclick | script | Triggers on a mouse double-click |
| ondrag | script | Triggers when an element is dragged |
| ondragend | script | Triggers at the end of a drag operation |
| ondragenter | script | Triggers when an element has been dragged to a valid drop target |
| ondragleave | script | Triggers when an element is being dragged over a valid drop target |
| ondragover | script | Triggers at the start of a drag operation |
| ondragstart | script | Triggers at the start of a drag operation |
| ondrop | script | Triggers when dragged element is being dropped |
| ondurationchange | script | Triggers when the length of the media is changed |
| onemptied | script | Triggers when a media resource element suddenly becomes empty. |
| onended | script | Triggers when media has reach the end |
| onerror | script | Triggers when an error occur |
| onfocus | script | Triggers when the window gets focus |
| onformchange | script | Triggers when a form changes |
| onforminput | script | Triggers when a form gets user input |
| onhaschange | script | Triggers when the document has change |
| oninput | script | Triggers when an element gets user input |
| oninvalid | script | Triggers when an element is invalid |
| onkeydown | script | Triggers when a key is pressed |
| onkeypress | script | Triggers when a key is pressed and released |
| onkeyup | script | Triggers when a key is released |
| onload | script | Triggers when the document loads |
| onloadeddata | script | Triggers when media data is loaded |
| onloadedmetadata | script | Triggers when the duration and other media data of a media element is loaded |
| onloadstart | script | Triggers when the browser starts to load the media data |
| onmessage | script | Triggers when the message is triggered |
| onmousedown | script | Triggers when a mouse button is pressed |
| onmousemove | script | Triggers when the mouse pointer moves |
| onmouseout | script | Triggers when the mouse pointer moves out of an element |
| onmouseover | script | Triggers when the mouse pointer moves over an element |
| onmouseup | script | Triggers when a mouse button is released |
| onmousewheel | script | Triggers when the mouse wheel is being rotated |
| onoffline | script | Triggers when the document goes offline |
| onoine | script | Triggers when the document comes online |
| ononline | script | Triggers when the document comes online |
| onpagehide | script | Triggers when the window is hidden |
| onpageshow | script | Triggers when the window becomes visible |
| onpause | script | Triggers when media data is paused |
| onplay | script | Triggers when media data is going to start playing |
| onplaying | script | Triggers when media data has start playing |
| onpopstate | script | Triggers when the window's history changes |
| onprogress | script | Triggers when the browser is fetching the media data |
| onratechange | script | Triggers when the media data's playing rate has changed |
| onreadystatechange | script | Triggers when the ready-state changes |
| onredo | script | Triggers when the document performs a redo |
| onresize | script | Triggers when the window is resized |
| onscroll | script | Triggers when an element's scrollbar is being scrolled |
| onseeked | script | Triggers when a media element's seeking attribute is no longer true, and the seeking has ended |
| onseeking | script | Triggers when a media element's seeking attribute is true, and the seeking has begun |
| onselect | script | Triggers when an element is selected |
| onstalled | script | Triggers when there is an error in fetching media data |
| onstorage | script | Triggers when a document loads |
| onsubmit | script | Triggers when a form is submitted |
| onsuspend | script | Triggers when the browser has been fetching media data, but stopped before the entire media file was fetched |
| ontimeupdate | script | Triggers when media changes its playing position |
| onundo | script | Triggers when a document performs an undo |
| onunload | script | Triggers when the user leaves the document |
| onvolumechange | script | Triggers when media changes the volume, also when volume is set to "mute" |
| onwaiting | script | Triggers when media has stopped playing, but is expected to resume |
