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?

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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.