Check/Uncheck all checkboxes

Question

I've seen many check/uncheck all checkboxes scripts. But far most does not respect that if I toggled all checkboxes using the "checked all"-checkbox and then uncheck a single one in the list, the "checked all" checkbox is still checked.

Is there an elegant way of handling this case?

Answer 1

$('#checkAll').click(function() {
    if(this.checked) {
        $('input:checkbox').attr('checked', true);
    }
    else {
        $('input:checkbox').removeAttr('checked');
    }
});

$('input:checkbox:not(#checkAll)').click(function() {
    if(!this.checked) {
        $('#checkAll').removeAttr('checked');
    }
    else {
        var numChecked = $('input:checkbox:checked:not(#checkAll)').length;
        var numTotal = $('input:checkbox:not(#checkAll)').length;
        if(numTotal == numChecked) {
            $('#checkAll').attr('checked', true);
        }
    }
});

Demo: http://jsfiddle.net/ThiefMaster/HuM4Q/

As pointed out in the question's comment, a regular checkbox is not perfect for this. My implementation disables the "check all" box as soon as one checkbox is unchecked. So, to uncheck all still-checked checkboxes you'll have to click twice (first to re-check the unchecked ones and then to uncheck all other ones). However, with a tri-state checkbox this might still be necessary as the state order might be unchecked->indefinite->checked->unchecked, so you'd need two clicks to come from indefinite to unchecked.

---

Since you probably don't want to check ALL checkboxes on your page with "Check All", replace input:checkbox with e.g. .autoCheckBox or input.autoCheckBox:checkbox and give those checkboxes class="autoCheckBox".

If you want all checkboxes inside a certain form, simple use #idOfYourForm input:checkbox or form[name=nameOfYourForm] input:checkbox

Answer 2

You can achieve this by attaching a click handler to each of the target checkboxes, and have that handler un-check the "control" checkbox based on the collective state of those target checkboxes. So, something like this:

// Control checks/unchecks targets
$('#controlcheckbox').click( function(){
  $('.targetcheckboxes').attr('checked', this.checked );
});

// Targets affect control
$('.targetcheckboxes').click( function(){
  if( $('.targetcheckboxes:not(:checked)').length ){
    $('#controlcheckbox').attr('checked',false);
  }
});

Even better -- you could attach this logic to an enclosing container element, and watch for the event using .delegate():

$('#some_container').delegate('.targetcheckboxes','click',function(){...} );