checkbox select all

checkall.js

$(function () {
    $('.checkall').on('click', function () {
        $(this).closest('fieldset').find(':checkbox').prop('checked', this.checked);
    });
});

checkbox-nesting.html

<fieldset>
    <!-- these will be affected by check all -->
    <div><input type="checkbox" class="checkall"> Check all</div>
    <div><input type="checkbox"> Checkbox</div>
    <div><input type="checkbox"> Checkbox</div>
    <div><input type="checkbox"> Checkbox</div>
</fieldset>
<fieldset>
    <!-- these won't be affected by check all; different field set -->
    <div><input type="checkbox"> Checkbox</div>
    <div><input type="checkbox"> Checkbox</div>
    <div><input type="checkbox"> Checkbox</div>
</fieldset>