Event Handling in JavaScript -oracleappshelp.com

The blog provides the details on the Event Handling in JavaScript. The Front End application allows user to perform action on the available data like user clicks on a button, user enters the data, user press a particular key, user moves the mouse, user closes the window, etc..

The action performed by the user when the state of the object is changed, known as Event. The JavaScript captures these events and allows the execution. This process is known as Event Handling.

JavaScript Libraries like React.js , Vue.js, Angular.js provides the Event and Event Handling as these libraries uses JavaScript.

The generated HTML element contains the set of events which can trigger JavaScript Code.
JavaScript Events are a part of the Document Object Model (DOM) Level 3.

The below given are the HTML Event Handlers as per the HTML 4.01 specification.

<form> Level Events

The below given are the events which can be triggered on the Form Level

Form Attribute	Description
onchange	triggers when the element changes
onsubmit	triggers when the form is submitted
onreset	triggers when the form is reset
onselect	triggers when the element is selected
onblur	triggers when the element loses focus
onfocus	triggers when the element gets focus

<body> Level Events

The below given are the events which can be triggered on the Body or the Frameset Level

Body Attribute	Description
onload	triggers when a HTML document loads
onunload	triggers when a HTML document unloads
onresize	triggers when browser window is resized

Keyboard Events

The below given are the events which can be triggered on the Keyboard Level

Keyboard Attribute	Description
onkeydown	triggers when key is pressed
onkeypress	triggers when key is pressed and released
onkeyup	triggers when key is released

Mouse Events

Mouse Attribute	Description
onclick	triggers when a mouse click
ondblclick	triggers when a mouse double-click
onmousedown	triggers when mouse button is pressed
onmousemove	triggers when mouse pointer moves
onmouseout	triggers when mouse pointer moves out of an element
onmouseover	triggers when mouse pointer moves over an element
onmouseup	triggers when mouse button is released

onClick Event Type Example in JavaScript

onClick Event Type is the most commonly used event in the UI application. Whenever the user click on the HTML elements the onClick event is triggered. The onClick event can be used to capture user input, perform form validations, displaying waning messages, etc.

<!DOCTYPE html>  
<html>  
<head>  
<script>  
function userMsg() {  
	alert("The onClick Event Message is displayed when user clicks button ");  
}  
</script>  
</head>  
<body>
 
<h3> JavaScript - onClick Event Type Example </h3>  
<button onclick = "userMsg()">Click me</button>  
</body>  
</html>

The below given is another onClick event in the paragraph element.

<HTML>
<HEAD>
</HEAD>
<BODY>
<h3> JavaScript - onClick Event Type Example </h3>  
<p id = "root">Click me</p>  
<script>  
document.getElementById("root").onclick = function() {  userMsg()  };  

function userMsg() {  
document.getElementById("root").innerHTML = "The onClick Event Message is displayed when user clicks button ";  
document.getElementById("root").style.color = "Blue";  
document.getElementById("root").style.backgroundColor = "Grey";  
document.getElementById("root").style.fontSize = "15px";  
document.getElementById("root").style.border = "4px solid Grey";   
}  
</script>  

</BODY>
</HTML>

onSubmit Event Type Example

When the Front End Application performs the “Submit” button, the onSubmit event type is triggered which could be used to validate the entered form details, submit request data as per the given action, displaying error and success messages, etc..

<html>
   <head>   
      <script type = "text/javascript">
            function validateFormDetails() {
			alert("Validate method executes with onSubmit Event Type ");  
            }
      </script>      
   </head>
   
   <body>  
<h3> JavaScript - onSubmit Event Type Example </h3>    
      <form method = "POST" action = "" onsubmit = "return validateFormDetails()">
         <input type = "submit" value = "Submit" />
      </form>      
   </body>
</html>

HTML5 Standard Events

The below given is the complete list of events supported as part of HTML5 specification

Attribute	Description
Offline	Triggers when the document goes offline
Onabort	Triggers on an abort event
onafterprint	Triggers after the document is printed
onbeforeonload	Triggers before the document loads
onbeforeprint	Triggers before the document is printed
onblur	Triggers when the window loses focus
oncanplay	Triggers when media can start play, but might has to stop for buffering
oncanplaythrough	Triggers when media can be played to the end, without stopping for buffering
onchange	Triggers when an element changes
onclick	Triggers on a mouse click
oncontextmenu	Triggers when a context menu is triggered
ondblclick	Triggers on a mouse double-click
ondrag	Triggers when an element is dragged
ondragend	Triggers at the end of a drag operation
ondragenter	Triggers when an element has been dragged to a valid drop target
ondragleave	Triggers when an element is being dragged over a valid drop target
ondragover	Triggers at the start of a drag operation
ondragstart	Triggers at the start of a drag operation
ondrop	Triggers when dragged element is being dropped
ondurationchange	Triggers when the length of the media is changed
onemptied	Triggers when a media resource element suddenly becomes empty.
onended	Triggers when media has reach the end
onerror	Triggers when an error occur
onfocus	Triggers when the window gets focus
onformchange	Triggers when a form changes
onforminput	Triggers when a form gets user input
onhaschange	Triggers when the document has change
oninput	Triggers when an element gets user input
oninvalid	Triggers when an element is invalid
onkeydown	Triggers when a key is pressed
onkeypress	Triggers when a key is pressed and released
onkeyup	Triggers when a key is released
onload	Triggers when the document loads
onloadeddata	Triggers when media data is loaded
onloadedmetadata	Triggers when the duration and other media data of a media element is loaded
onloadstart	Triggers when the browser starts to load the media data
onmessage	Triggers when the message is triggered
onmousedown	Triggers when a mouse button is pressed
onmousemove	Triggers when the mouse pointer moves
onmouseout	Triggers when the mouse pointer moves out of an element
onmouseover	Triggers when the mouse pointer moves over an element
onmouseup	Triggers when a mouse button is released
onmousewheel	Triggers when the mouse wheel is being rotated
onoffline	Triggers when the document goes offline
onoine	Triggers when the document comes online
ononline	Triggers when the document comes online
onpagehide	Triggers when the window is hidden
onpageshow	Triggers when the window becomes visible
onpause	Triggers when media data is paused
onplay	Triggers when media data is going to start playing
onplaying	Triggers when media data has start playing
onpopstate	Triggers when window history changes
onprogress	Triggers when the browser fetches the media data
onratechange	Triggers when the media data’s playing rate has changed
onreadystatechange	Triggers when the ready-state changes
onredo	Triggers when a redo operation is performed
onresize	Triggers on the window resize
onscroll	Triggers when an element’s scrollbar is being scrolled
onseeked	Triggers when a media element’s seeking attribute is no longer true, and the seeking has ended
onseeking	Triggers when a media element’s seeking attribute is true, and the seeking has begun
onselect	Triggers when an element is selected
onstalled	Triggers when there is an error in fetching media data
onstorage	Triggers when a document loads
onsubmit	Triggers when a form is submitted
onsuspend	Triggers when the browser action is suspended
ontimeupdate	Triggers when media changes its playing position
onundo	Triggers when a undo operation is performed
onunload	Triggers when the user leaves the document
onvolumechange	Triggers when media changes the volume, also when volume is set to “mute”
onwaiting	Triggers when media has stopped playing, but is expected to resume