Radio Button Object, dom Radiobutton events

Tutorials

Javascript

Topic

How to change Radio Button selection using javascript?
or
What are the events associated with Radiobutton?

Explanation

Basics of HTML form radiobutton

Radio Button Object :
The following syntax will get the Radio Button object in javascript
Syntax: document.formname.radioname

Example Code:
<form name=testform>
<input name=rb1 value=test type=radio>
<input name=rb2 value=test2 type=radio>
</form>

<script language="javascript">
var rbobject= document.testform.rb1;
</script>

The object rbobject is an array of radio elements. To use the first radio button, we have to call rbobject[0], for second box it is rbobject[1] and so on. Here are the events, dom properties and method associated with Radio Button element.

Event Handlers: Associated with Form type Radio Button:
All the examples below use a javascript function output
<script language=javascript>
function output()
{
alert("testing RadioButton events");
}
</script>

Event Handler	Description	Example
onMouseOver	This is invoked when a mouse is moved over the Radio Button	<input type=radio onMouseOver="output()"> Result: CB1
onMouseDown	This is invoked when a mouse is pressed down on the Radiobutton	<input type=radio onMouseDown="output()"> Result: CB1
onMouseUp	This is invoked when a mouse is pressed down on the radio and released	<input type=radio onMouseUp="output()"> Result: CB1
onClick	This is invoked when a mouse click is done on the radio	<input type=radio onClick="output()"> Result: CB1
onBlur	Executes some code when the Radio Button loses focus using tab	<input type=radio onBlur="output()"> Result: CB1
onFocus	Executes some code when the radio button gets the focus using tab	<input type=radio onFocus="output()"> Result: CB1

DOM Properties:
The following are the list of DOM (Dynamic Object Model) properties that can be used to get and alter RadioButton properties in javascript.
The below examples are based on the form
<form name=testrb>
<input name=myrb1 type=radio value=xxx> Checking 1
<input name=myrb2 type=radio value=xxx> Checking 2
</form>

DOM Property	Description	Example
checked	Used to check or select RadioButton selection	To Check: var ss = document.testb.myrb[0].checked; To Select: document.testb.myrb[1].checked = true; This will select second element.
defaultChecked	Used to check whether the Radio Button is checked by default	To Get: var ss = document.testb.myrb[0].defaultChecked;
form	Used to get the parent node (form object) of this RadioButton	To Get: var ss = document.testb.myrb[0].form;
name	Used to get Radio Button name	To Get: var ss = document.testb.myrb[0].name;
type	Used to get form type	To Get: var ss = document.testb.myrb[0].type;
value	Used to set or get RadioButton value	To Get: var ss = document.testb.myrb[0].value; To Set:: document.testb.myrb[0].value = "testy";

DOM Methods:
The following are the list of DOM (Dynamic Object Model) methods that can be used to do dynamic changes like dynamic Radiobutton selection using javascript.

DOM Method	Description	Example
click()	Used to dynamically make a Radio Button checked	To Click: document.testb.myrb.click();
blur()	Used to dynamically make the Radio Button blur	To Blur: document.testb.myrb.blur();
focus()	Used to dynamically get focus on the Radio Button	To Focus: document.testb.myrb.focus();

Example: Making Radiobutton Select on Mouse Over

Result: