Here are 10 examples of styling radio button like an On-Off switch. There is no need to put an extra class handled by JavaScript the CSS handles it all.

iOS 6 switch style

CSS3 Toggle Switch

Stylish CSS Switch Buttons

On/Off FlipSwitch

CSS3 Flip Switch

umbrUI

Button Switches with Checkboxes and CSS3 Fanciness

CSS switch and push button

Switch iOS Icon

CSS Toggle Switches