使用javascript验证动态数量的复选框

Question

I have some ASP code which presents any where from 1-any number of checkboxes (which are named the same) on the page. This validation does work however I think its a bit weak:

   if (document.getElementById('selectedDocs').checked)
   {
       //this is here to handle the situation where there is only one checkbox being displayed
   }
   else
  {
      var checked = false; 
  var field = myForm.selectedDocs; 
  for(var j = 0; j < field.length; j++)
  { 
     if(field[j].checked == true)
     { 
        checked = true; 
        break; 
     } 
  } 
  if(!checked)
  { 
     alert("You have not ticked any options.  At least one must be selected to proceed!") 
     return false; 
  }    
}

I was working with the code in the else block but this only works when there is more than one checkbox. It ignores the fact I have ticked the one single option when there is only one. So I placed the code inside the if section......Although it woks its a bit of a hack, can someone kindly improve it for me?

Thanking you...

Answer 1

Use:

var field = myForm.getElementsByName('selectedDocs');

This always returns a NodeList that you can iterate over.

Answer 2

If they are in a form and all have the same name, they can be accessed as a collection that is a property of the form. So given:

<form id="f0" ...>
  <input type="checkbox" name="cb0" ...>
  <input type="checkbox" name="cb0" ...>
  <input type="checkbox" name="cb0" ...>
  ...
</form>

All the following return a reference to the form:

var form = document.getElementById('f0');

var form = document.forms['f0'];

var form = document.forms[0];  // if first form in document

and and all the following return a collection of the checkboxes named "cb0":

var checkboxes = form.cb0

var checkboxes = form['cb0'];

var checkboxes = form.elements.['cb0'];