Question

How can I remove the "disabled='disabled' attribute of submit button with id='bla' if at least one checkbox with class='check' is checked?

If no checkboxes are checked, the disabled attribute should return to the submit button.

Answer 1

EDIT (11-01-2021) – As pointed out by @Janus Bahs Jacquet, as of jQuery 1.6.1, properties of elements should be manipulated using the .prop() method instead of .attr() method.

$('.check').change(function() {
    if ($('.check:checked').length) {
        $('#sub').removeAttr('disabled');
    } else {
        $('#sub').props('disabled', true);
    }
});

Updated demo : http://jsfiddle.net/kjb0fyr8/

---

You just need to check the length property of the checked array

$('.check').change(function() {
    if ($('.check:checked').length) {
        $('#sub').removeAttr('disabled');
    } else {
        $('#sub').attr('disabled', 'disabled');
    }
});

Here’s the demo : http://jsfiddle.net/LUnN5/