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23/02/2014 Categories: Javascript. No Comments on Event Handling in Javascript

The programming which allows computations based on the activities in a browser or by the activities performed by the user on the elements in a document is known as event-driven programming.

An event is the specification (essentially an object created by the browser and JavaScript) of something significant has occurred. Examples of events are click, submit, keyup etc. In JavaScript all the event names are specified in lowercase. An event handler (essentially a function) is a set of statements (code) that handles the event.

Below table lists most commonly used events and their associated tag attributes:

Event Tag Attribute
blur onblur
change onchange
click onclick
dblclick ondblclick
focus onfocus
keydown onkeydown
keypress onkeypress
keyup onkeyup
load onload
mousedown onmousedown
mouseup onmouseup
mousemove onmousemove
mouseover onmouseover
mouseout onmouseout
reset onreset
select onselect
submit onsubmit
unload onunload

Below table lists event attributes and their corresponding tags in HTML:

Attribute Tag Description
onblur <a>

<button>

<input>

<textarea>

<select>

The link looses input focus

The button looses input focus

The input element looses focus

The text area looses focus

The selection element looses focus

onchange <input>

<textarea>

<select>

The input element is changed and looses focus

The text area changes and looses focus

The selection element is changed and looses focus

onclick <a>

<input>

The user clicks on the link

The input element is clicked

ondblclick Most elements The user double clicks the mouse left button
onfocus <a>

<input>

<textarea>

<select>

The link acquires focus

The input element acquires focus

A text area acquires focus

A selection element acquires focus

onkeydown <body>

form elements

A key is pressed down
onkeypress <body>

form elements

A key is pressed down and released
onkeyup <body>

form elements

A key is released
onload <body> The document finished loading
onmousedown Most elements The user clicks the left mouse button
onmouseup Most elements The left mouse button is released
onmousemove Most elements The user moves the mouse cursor on the element
onmouseover Most elements The mouse cursor is moved over the element
onmouseout Most elements The mouse cursor is moved away from the element
onreset <form> The reset button is clicked
onselect <input>

<textarea>

The mouse cursor is moved over the element

The text is selected within the text area

onsubmit <form> The submit button is pressed
onunload <body> The user exits the document

The process of linking an event handler with an event is known as registration. There are two ways to register an event handler in DOM 0 event model. First way is by assigning the event handler script to an event tag attribute as shown below:

<input   type=”button”  value=”Click Me”  onclick=”func1( );” />

In the above code, the event handler func1 is assigned to the event attribute onclick of a button.

The second way is by assigning the event handler to the event property of the element as shown below:

document.getElementById(ID_of_element).onclick = func1;

Suryateja Pericherla

Suryateja Pericherla

Hello, I am Suryateja Pericherla working as an Asst. Professor in CSE department at Vishnu Institute of Technology. I write articles to share my knowledge and make people knowledgeable regarding certain topics.
Suryateja Pericherla

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