Javascript null error

[[email protected]]

I get error:
"Object required" Code 0 (in IE8)

"Error: document.getElementById("buy_block") is null
Source File: http://alacartedancewear.com/themes/crystals/js/product.js" (in Firefox)

from the following code (right after the first { ):

function updateBeltSelect(id_attribute)
{belton=document.getElementById('buy_block').group_3.value;
if (belton == 21) $("#group_3").val(id_attribute);
else $("#group_3").val('(no belt)');
}



I know the value starts out as null, and I have defined belton. Not sure how to deal with it because I check for null value and still get same error.

[[email protected]]

Thanks, but I still get same error right at beginning of your suggested line, and evin if I do a conditional for null or even
if (document.getElementById(‘buy_block’).group_3.value) ...
to check if defined.

[[email protected]]

Yes, I said the FireFox error:
“Error: document.getElementById(“buy_block”) is null
Source File: http://alacartedancewear.com/themes/crystals/js/product.js” (in Firefox)

I agree, also, and I have worked around it, given that the first time the function gets called with a conditional on the passed value I avoid referencing it altogether. Works great now. Thanks for your help!