It’s a common problem with a dozen different solutions – if you’ve ever needed to add a ‘select all’ checkbox to a form in order to make your users’ lives easier then you’ll have searched for a simple way to do it. If you’re using jQuery here’s a very simple method that’s as easy as can be:

You can replace the form identifier with whatever container you choose (fieldset can be useful if your form is split up like that). This code will cause all the checkboxes in the form to be toggled when you toggle any checkbox that has the selectall class.

Simple.

UPDATE: Modified code to be slightly more efficient as suggested by Jamy Golden.