Javascript Get or Set Checked Radio Value

 

Description

This pair of Javascript function can get or set the checked value of a group of radio buttons.  These functions are specially designed for dynamic pages, and work without error with zero, one, or more radio buttons.  Also, because the radio length is saved before looping, this function is much faster.  Finally, the functions are granted to the public domain.

Source Code

// return the value of the radio button that is checked
// return an empty string if none are checked, or
// there are no radio buttons
function getCheckedValue(radioObj) {
	if(!radioObj)
		return "";
	var radioLength = radioObj.length;
	if(radioLength == undefined)
		if(radioObj.checked)
			return radioObj.value;
		else
			return "";
	for(var i = 0; i < radioLength; i++) {
		if(radioObj[i].checked) {
			return radioObj[i].value;
		}
	}
	return "";
}

// set the radio button with the given value as being checked
// do nothing if there are no radio buttons
// if the given value does not exist, all the radio buttons
// are reset to unchecked
function setCheckedValue(radioObj, newValue) {
	if(!radioObj)
		return;
	var radioLength = radioObj.length;
	if(radioLength == undefined) {
		radioObj.checked = (radioObj.value == newValue.toString());
		return;
	}
	for(var i = 0; i < radioLength; i++) {
		radioObj[i].checked = false;
		if(radioObj[i].value == newValue.toString()) {
			radioObj[i].checked = true;
		}
	}
}

Example

Use the view source command in your browser to see how the code below works.  Note the use of the label HTML tag with a style that gives it a border and background color. You should always use the label tag with radio buttons. This signals to the user that the whole boxed area may be clicked to set the radio button, rather than just the tiny circle.

If you are using a scripting language like PHP, ColdFusion, or ASP, then write a function that prints your radio buttons from an array.  It can automatically write the for and id properties by concatenating the radio name and value.

Zero One Two Three Four