How do you change an HTML radiobutton selection from Javascript?

I开发者_如何学Go need to select an HTML radiobutton (deselecting any previously selected radiobutton) on my form, from within Javascript.

How is this accomplished?

If you set the "checked" property to true on one radio button, the other button with the same name is automatically unchecked.

Thus,

document.getElementById('buttonX').checked = true;

will cause "buttonY" to be unchecked if the HTML looks like:

<input type='radio' id='buttonX' name='fred' value='X'>
<input type='radio' id='buttonY' name='fred' value='Y' checked>

edit Remember that "radio buttons" have that name because on old radios (not necessarily older than me) the station preset buttons were mechanically inter-linked such that exactly one button was pressed at all times. Fiddling with the buttons to get them all to be un-pressed was a fun but risky pastime, as most adults didn't appreciate the aesthetic appeal of a row of un-pressed radio buttons all neatly aligned.