What is an Event in JavaScript?
JavaScript's
interaction with HTML is handled through events that occur when the user or the
browser manipulates a page.
When the page loads, it
is called an event. When the user clicks a button, that click too is an event.
Other examples include events like pressing any key, closing a window, resizing
a window, etc.
Developers can use
these events to execute JavaScript coded responses, which cause buttons to
close windows, messages to be displayed to users, data to be validated, and
virtually any other type of response imaginable.
Events are a part of
the Document Object Model (DOM) Level 3 and every HTML element contains a set
of events which can trigger JavaScript Code.
Please go through this
small tutorial for a better understanding HTML
Event. Here we
will see a few examples to understand the relation between Event and
JavaScript.
onclick Event Type
This is the most
frequently used event type which occurs when a user clicks the left button of
his mouse. You can put your validation, warning etc., against this event type.
Example
Try the following example.
<html>
<head>
<script type="text/javascript">
<!--
function sayHello() {
document.write ("Hello World")
}
//-->
</script>
</head>
<body>
<p> Click the following button and see
result</p>
<input type="button"
onclick="sayHello()" value="Say Hello" />
</body>
</html>
Output
Click the following button and see result
Say Hello
onsubmit Event Type
onsubmit
is an
event that occurs when you try to submit a form. You can put your form validation against this
event type.
Example
The following example shows how to use
onsubmit. Here a validate() function
before submitting a form data to
we are
calling the webserver.
If validate()
function returns true, the form will be submitted, otherwise it will not submit
the data.
Try the following example.
<html>
<head>
<script
type="text/javascript">
<!--
function validation() {
all validation goes here
.........
return either true or false
}
//-->
</script>
</head>
<body>
<form method="POST"
action="t.cgi" onsubmit="return validate()">
.......
<input type="submit"
value="Submit" />
</form>
</body>
</html>
onmouseover and onmouseout
These two event types
will help you create nice effects with images or even with text as well. The onmouseover event triggers when you
bring your mouse over any element and the onmouseout
triggers when you move your mouse out from that element. Try the following
example.
<html>
<head>
<script
type="text/javascript">
<!--
function over() {
document.write ("Mouse Over");
}
function out() {
document.write ("Mouse Out");
}
//-->
</script>
</head>
<body>
<p>Bring your mouse inside the
division to see the result:</p> <div onmouseover="over()"
onmouseout="out()">
<h2> This is inside the division
</h2>
</div>
</body>
</html>
Output
Bring your mouse inside the division to see
the result:
This is inside
the division
HTML 5 Standard Events
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 leaves a valid drop
|
|
|
|
target
|
|
|
|
|
|
ondragover
|
script
|
Triggers
when an element
is being dragged
|
|
|
|
over a valid drop target
|
|
|
|
|
|
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
|
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