How to validate a form with multiple checkboxes to have atleast one checked

I'm trying to validate a form using the validate plugin for jquery. I want to require that the user check at least one checkbox in a group in order for the form to be submitted. Here's my jquery code:

$().ready(function() {
$("#subscribeForm").validate({
   rules:   { list: {required: "#list0:checked"} },
   messages:  { list:  "Please select at least one newsletter"}                                                        
 });
 });

and here's the html form:

<form action="" method="GET" id="subscribeForm">
<fieldset id="cbgroup">
    <div><input name="list" id="list0" type="checkbox"  开发者_开发问答value="newsletter0" >zero</div>
    <div><input name="list" id="list1" type="checkbox"  value="newsletter1" >one</div>
    <div><input name="list" id="list2" type="checkbox"  value="newsletter2" >two</div>
</fieldset>
<input name="submit" type="submit"  value="submit">

The problem is that the form submits even if nothing is checked. How can I resolve this?

---

  $('#subscribeForm').validate( {
      rules: {
          list: {
              required: true,
              minlength: 1
          }
       }
   });

I think this will make sure at least one is checked.

---

This script below should put you on the right track perhaps?

You can keep this html the same (though I changed the method to POST):

<form method="POST" id="subscribeForm">
    <fieldset id="cbgroup">
        <div><input name="list" id="list0" type="checkbox"  value="newsletter0" >zero</div>
        <div><input name="list" id="list1" type="checkbox"  value="newsletter1" >one</div>
        <div><input name="list" id="list2" type="checkbox"  value="newsletter2" >two</div>
    </fieldset>
    <input name="submit" type="submit"  value="submit">
</form>

and this javascript validates

function onSubmit() 
{ 
    var fields = $("input[name='list']").serializeArray(); 
    if (fields.length === 0) 
    { 
        alert('nothing selected'); 
        // cancel submit
        return false;
    } 
    else 
    { 
        alert(fields.length + " items selected"); 
    }
}

// register event on form, not submit button
$('#subscribeForm').submit(onSubmit)

and you can find a working example of it here

UPDATE (Oct 2012)
Additionally it should be noted that the checkboxes must have a "name" property, or else they will not be added to the array. Only having "id" will not work.

UPDATE (May 2013)
Moved the submit registration to javascript and registered the submit onto the form (as it should have been originally)

UPDATE (June 2016)
Changes == to ===

---

How about this:

$(document).ready(function() {
    $('#subscribeForm').submit(function() {
        var $fields = $(this).find('input[name="list"]:checked');
        if (!$fields.length) {
            alert('You must check at least one box!');
            return false; // The form will *not* submit
        }
    });
});

---

The above addMethod by Lod Lawson is not completely correct. It's $.validator and not $.validate and the validator method name cb_selectone requires quotes. Here is a corrected version that I tested:

$.validator.addMethod('cb_selectone', function(value,element){
    if(element.length>0){
        for(var i=0;i<element.length;i++){
            if($(element[i]).val('checked')) return true;
        }
        return false;
    }
    return false;
}, 'Please select at least one option');

---

Here is the a quick solution for multiple checkbox validation using jquery validation plugin:

jQuery.validator.addMethod('atLeastOneChecked', function(value, element) {
  return ($('.cbgroup input:checked').length > 0);
});

$('#subscribeForm').validate({
  rules: {
    list0: { atLeastOneChecked: true }
  },
  messages: {
    list0: { 'Please check at least one option' }
  }
});

$('.cbgroup input').click(function() {
  $('#list0').valid();
});

---

if (
  document.forms["form"]["mon"].checked==false &&
  document.forms["form"]["tues"].checked==false &&
  document.forms["form"]["wed"].checked==false &&
  document.forms["form"]["thrs"].checked==false &&
  document.forms["form"]["fri"].checked==false
) {
  alert("Select at least One Day into Five Days");
  return false; 
}

---

Good example without custom validate methods, but with metadata plugin and some extra html.

Demo from Jquery.Validate plugin author

---

How about this

$.validate.addMethod(cb_selectone,
                   function(value,element){
                           if(element.length>0){
                               for(var i=0;i<element.length;i++){
                                if($(element[i]).val('checked')) return true;
                               }
                           return false;
                           }
                            return false;
                  },
                  'Please select a least one')

Now you ca do

$.validate({rules:{checklist:"cb_selectone"}});

You can even go further a specify the minimum number to select with a third param in the callback function.I have not tested it yet so tell me if it works.

---

I had to do the same thing and this is what I wrote.I made it more flexible in my case as I had multiple group of check boxes to check.

// param: reqNum number of checkboxes to select
$.fn.checkboxValidate = function(reqNum){
    var fields = this.serializeArray();
    return (fields.length < reqNum) ? 'invalid' : 'valid';
}

then you can pass this function to check multiple group of checkboxes with multiple rules.

// helper function to create error
function err(msg){
    alert("Please select a " + msg + " preference.");
}

$('#reg').submit(function(e){
    //needs at lease 2 checkboxes to be selected
    if($("input.region, input.music").checkboxValidate(2) == 'invalid'){
        err("Region and Music");
    } 
});

---

I had a slighlty different scenario. My checkboxes were created in dynamic and they were not of same group. But atleast any one of them had to be checked. My approach (never say this is perfect), I created a genric validator for all of them:

jQuery.validator.addMethod("validatorName", function(value, element) {
    if (($('input:checkbox[name=chkBox1]:checked').val() == "Val1") ||
        ($('input:checkbox[name=chkBox2]:checked').val() == "Val2") ||
        ($('input:checkbox[name=chkBox3]:checked').val() == "Val3")) 
    {   
        return true;
    }
    else
    {
        return false;
    }       
}, "Please Select any one value");

Now I had to associate each of the chkbox to this one single validator.

Again I had to trigger the validation when any of the checkboxes were clicked triggering the validator.

$('#piRequest input:checkbox[name=chkBox1]').click(function(e){
    $("#myform").valid();
});

---

I checked all answers and even in other similar questions, I tried to find optimal way with help of html class and custom rule.

my html structure for multiple checkboxes are like this

$.validator.addMethod('multicheckbox_rule', function (value, element) {
			var $parent = $(element).closest('.checkbox_wrapper');
			if($parent.find('.checkbox_item').is(':checked')) return true;
            return false;
}, 'Please at least select one');

<div class="checkbox_wrapper">
<label for="checkbox-1"><input class="checkbox_item" id="checkbox-1"  name="checkbox_item[1]" type="checkbox" value="1" data-rule-multicheckbox_rule="1" /> Checkbox_item 1</label>
<label for="checkbox-2"><input class="checkbox_item" id="checkbox-2" name="checkbox_item[2]" type="checkbox" value="1" data-rule-multicheckbox_rule="1" /> Checkbox_item 1</label>
</div>