how do i validate this - radio button

[ZUWARI]

on my form i got four radio button and i want my user to choose this radio button before they submit it.

what i do:
i create a function named

validateRadio(form)
{
if (form.radiobtt.checked)
{}else
{alert("you must choose one of this radio button");
return false;
}

but with this function, i got error telling me that 'the object does'nt support this....

what wrong and how should i code it the right way

(question from newbie )

[DeadEyes]

try this

function validateRadio(){ 
 if (!document.frm.rdo.checked)
	alert('not checked');
 return false;
}

[ZUWARI]

it works but....

this is my full function:

for (Count = 0; Count < 2; Count++)
{
if (document.frm.frmHakMlk.checked)
{}
else
{
alert ("Please choose your option");
return false;
}

}

but when i click one of the radio button the result is still the same.
it seem that when the user choose the radio button, the function cannot read it. even can't test it! what happend?

[DeadEyes]

Do you have more than one radio button with the same name?
if so then it's an array and should be handled:

document.frm.frmHakMlk[count].checked

[ZUWARI]

OPPS... silly me....

yeah it should be that way. but i just modify it...
not good but ok

if ((document.frm.frmHakMlk[0].checked)|| (document.frm.frmHakMlk[1].checked)|| (document.frm.frmHakMlk[2].checked))
{}
else
{
alert ("Please choose your option");
return false;
}

thanks DeadEye!

[CornedBee]

To make extension to more radios easier I recommend this function:

function IsCheckedRadio(rad, num)
{
  var ch, i;
  for(i=0;i<num;++i)
    ch = ch || rad[i].checked;
  return ch;
}

[CornedBee]

To implement this in your function you'd do

if(!IsCheckedRadio(document.frm.frmHakMlk, 3))
  alert("bla");