How can I preselect a radio button using javascript or jquery?

I know this is probably easy, but I just can't figure it out.

I am working with a SAAS shopping cart solution so I can't adjust the form code or use PHP, so I need to use javascript or jquery.

In this cart, I have a form....

<form method="post" action="cart.php" id="productDetailsAddToCartForm">  
Please Select a Bottle Size:  
<li><label><input name="variation[1]" type="radio" class="RadioButton" value="30"  /> 11oz</label></li> 
<li><label><input name="variation[1]" type="radio" class="RadioButton" value="31"  /> 33oz </label>  

And I need to preselect the first radio button using jquery or javascript.

Can you help?


You can use the attr method with checked like this:

$('.RadioButton:first').attr('checked', true);


$('.RadioButton:first').attr('checked', 'checked');

Note that :first will select the first radio button there.

$(':input:radio:eq(0)').attr('checked', 'checked');

This will check the first radio box on the page.

Need Your Help

sizeof(*this) in class definition


Can we do something like this:

jQuery ajax request to php, how to return plain text only

php jquery ajax xmlhttprequest

I am making an ajax request to a php page and I cannot for the life of me get it to just return plain text.