How to set radio button status with JavaScript

Question

What method would be best to use to selectively set a single or multiple radio button(s) to a desired setting with JavaScript?

Answer 1

Very simple

radiobtn = document.getElementById("theid"); radiobtn.checked = true; 

Answer 2

the form

<form name="teenageMutant">   <input value="aa" type="radio" name="ninjaTurtles"/>   <input value="bb" type="radio" name="ninjaTurtles"/>   <input value="cc" type="radio" name="ninjaTurtles" checked/> </form> 

value="cc" will be checked by default, if you remove the "checked" non of the boxes will be checked when the form is first loaded.

document.teenageMutant.ninjaTurtles[0].checked=true; 

now value="aa" is checked. The other radio check boxes are unchecked.

see it in action: http://jsfiddle.net/yaArr/

You may do the same using the form id and the radio button id. Here is a form with id's.

<form id="lizardPeople" name="teenageMutant">   <input id="dinosaurs" value="aa" type="radio" name="ninjaTurtles"/>   <input id="elephant" value="bb" type="radio" name="ninjaTurtles"/>   <input id="dodoBird" value="cc" type="radio" name="ninjaTurtles" checked/> </form> 

value="cc" is checked by default.

document.forms["lizardPeople"]["dinosaurs"].checked=true; 

now value="aa" with id="dinosaurs" is checked, just like before.

See it in action: http://jsfiddle.net/jPfXS/