Required checkbox

Provided that all three checkboxes have the same name, just use the built in cf validation ;

<cfinput type="checkbox" name="cars" value="Honda" required="yes" message="Please check at least one car">Honda <br>

<cfinput type="checkbox" name="cars" value="Ford"> Ford <br>

<cfinput type="chekcbox" name="cars" value="Toyota">Toyota

You can use JavaScript, server-side Cold Fusion code, or better yet, both. Remember, though, that JavaScript is only for user-friendly type of validation.In almost all cases, you really need to use server-side validation, because users can circumvent JavaScript. You can do the server-side validation in several ways, the code in the reply from gedecus will work well enough.

I googled 'javascript required checkbox' and found some good suggestions. Here's a simple one that looks good:

<SCRIPT TYPE="text/javascript" LANGUAGE=JAVASCRIPT>
 
function checkCheckBoxes() {
     if (document.frmTest.CHKBOX_1.checked == false &&
         document.frmTest.CHKBOX_2.checked == false &&
         document.frmTest.CHKBOX_3.checked == false)
          {
          alert ('You didn\'t choose any of the checkboxes!');
          return false;
          }
     else
          {
          return true;
          }
     }
//-->
</SCRIPT>
 


<form onsubmit="return checkCheckBoxes();" action="">
<input type="checkbox" name="CHKBOX_1" value="1">1</p>
<input type="checkbox" name="CHKBOX_2" value="2">2</p>
<input type="checkbox" name="CHKBOX_3" value="3">3</p>
<input type="submit" value="Submit!" />
</form>

There are many ways to do it. But it all really depends on what form validation you're using now.

You could do something like:

<cfif IsDefined("form.submit")>

     <cfif NOT IsDefined("form.checkbox1") AND NOT IsDefined("form.checkbox2") AND NOT IsDefined("form.checkbox3")>

          code to process form as error

     </cfif>

</cfif>

may be JavaScript is the answer.