JavaScript :: Events

What is an Event ?

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.

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.


Try the following example.

      <script type = "text/javascript">
            function sayHello() {
               alert("Hello World")
      <p>Click the following button and see result</p>      
         <input type = "button" onclick = "sayHello()" value = "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.


The following example shows how to use onsubmit. Here we are calling a validate() function before submitting a form data to the webserver. If validate() function returns true, the form will be submitted, otherwise it will not submit the data.

Try the following example.

      <script type = "text/javascript">
            function validation() {
               all validation goes here
               return either true or false
      <form method = "POST" action = "t.cgi" onsubmit = "return validate()">
         <input type = "submit" value = "Submit" />

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.Live Demo

      <script type = "text/javascript">
            function over() {
               document.write ("Mouse Over");
            function out() {
               document.write ("Mouse Out");
      <p>Bring your mouse inside the division to see the result:</p>      
      <div onmouseover = "over()" onmouseout = "out()">
         <h2> This is inside the division </h2>

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.

OfflinescriptTriggers when the document goes offline
OnabortscriptTriggers on an abort event
onafterprintscriptTriggers after the document is printed
onbeforeonloadscriptTriggers before the document loads
onbeforeprintscriptTriggers before the document is printed
onblurscriptTriggers when the window loses focus
oncanplayscriptTriggers when media can start play, but might has to stop for buffering
oncanplaythroughscriptTriggers when media can be played to the end, without stopping for buffering
onchangescriptTriggers when an element changes
onclickscriptTriggers on a mouse click
oncontextmenuscriptTriggers when a context menu is triggered
ondblclickscriptTriggers on a mouse double-click
ondragscriptTriggers when an element is dragged
ondragendscriptTriggers at the end of a drag operation
ondragenterscriptTriggers when an element has been dragged to a valid drop target
ondragleavescriptTriggers when an element is being dragged over a valid drop target
ondragoverscriptTriggers at the start of a drag operation
ondragstartscriptTriggers at the start of a drag operation
ondropscriptTriggers when dragged element is being dropped
ondurationchangescriptTriggers when the length of the media is changed
onemptiedscriptTriggers when a media resource element suddenly becomes empty.
onendedscriptTriggers when media has reach the end
onerrorscriptTriggers when an error occur
onfocusscriptTriggers when the window gets focus
onformchangescriptTriggers when a form changes
onforminputscriptTriggers when a form gets user input
onhaschangescriptTriggers when the document has change
oninputscriptTriggers when an element gets user input
oninvalidscriptTriggers when an element is invalid
onkeydownscriptTriggers when a key is pressed
onkeypressscriptTriggers when a key is pressed and released
onkeyupscriptTriggers when a key is released
onloadscriptTriggers when the document loads
onloadeddatascriptTriggers when media data is loaded
onloadedmetadatascriptTriggers when the duration and other media data of a media element is loaded
onloadstartscriptTriggers when the browser starts to load the media data
onmessagescriptTriggers when the message is triggered
onmousedownscriptTriggers when a mouse button is pressed
onmousemovescriptTriggers when the mouse pointer moves
onmouseoutscriptTriggers when the mouse pointer moves out of an element
onmouseoverscriptTriggers when the mouse pointer moves over an element
onmouseupscriptTriggers when a mouse button is released
onmousewheelscriptTriggers when the mouse wheel is being rotated
onofflinescriptTriggers when the document goes offline
onoinescriptTriggers when the document comes online
ononlinescriptTriggers when the document comes online
onpagehidescriptTriggers when the window is hidden
onpageshowscriptTriggers when the window becomes visible
onpausescriptTriggers when media data is paused
onplayscriptTriggers when media data is going to start playing
onplayingscriptTriggers when media data has start playing
onpopstatescriptTriggers when the window’s history changes
onprogressscriptTriggers when the browser is fetching the media data
onratechangescriptTriggers when the media data’s playing rate has changed
onreadystatechangescriptTriggers when the ready-state changes
onredoscriptTriggers when the document performs a redo
onresizescriptTriggers when the window is resized
onscrollscriptTriggers when an element’s scrollbar is being scrolled
onseekedscriptTriggers when a media element’s seeking attribute is no longer true, and the seeking has ended
onseekingscriptTriggers when a media element’s seeking attribute is true, and the seeking has begun
onselectscriptTriggers when an element is selected
onstalledscriptTriggers when there is an error in fetching media data
onstoragescriptTriggers when a document loads
onsubmitscriptTriggers when a form is submitted
onsuspendscriptTriggers when the browser has been fetching media data, but stopped before the entire media file was fetched
ontimeupdatescriptTriggers when media changes its playing position
onundoscriptTriggers when a document performs an undo
onunloadscriptTriggers when the user leaves the document
onvolumechangescriptTriggers when media changes the volume, also when volume is set to “mute”
onwaitingscriptTriggers when media has stopped playing, but is expected to resume

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