JavaScript Events

JavaScript Events


JavaScript Events
What is an Event
  • JavaScript interaction with HTML handled through events.
  • When the page loads, it is called an event. When the user clicks too is an event. Other examples include events like pressing any key, closing a Window, resizing a Window, etc.
  • HTML events are “things” that happen to html elements.
  • When JavaScript is used in HTML pages, Java can “react” to these events.
Event-driven Programs
  • Programs that can capture and respond to events are called ‘event-driven programs’
  • JavaScript was specifically designed for writing such programs
  • Almost all programs written in JavaScript are driven.
 
Event-driven Programming
JavaScript lets you execute code when events are detected.
Html allows event handler attributes, with JavaScript code, to be added to html elements.
Syntax
< some-HTML-element some-event=’Some JavaScript’>
Common HTML Events
There are some common HTML Events are as below table:
Event
 
Description
onchange
 
An HTML element has been changed
onclick
 
The user clicks an HTML element
onmouseover
 
The user moves the mouse over an HTML element
onmouseout
 
The user moves the mouse away from an HTML 
element
onkeydown
 
The user pushes a keyboard key
onload
 
The browser has finished loading the page
Summit
 
Fires When a form is submitted
Select
 
Fires when a text selection begins
resize
 
Fires When the size of an object changes
reset
 
Fire when form resets
 
Event Handler
The function that’s called when an event occurs is known as the event handler.
When a GUI (Graphical User Interface)  event occurs in a form , the browser calls the specified event handling function.
Before any event can be processed, each element must know which event –handling function will be called when a particular event occurs.