What's the best way to detect a 'touch screen' device using JavaScript?

Question

I\'ve written a jQuery plug-in that\'s for use on both desktop and mobile devices. I wondered if there is a way with JavaScript to detect if the device has touch screen capa

Answer 1

The practical answer seems to be one that considers the context:

1) Public site (no login)
Code the UI to work with both options together.

2) Login site
Capture whether a mouse-move occurred on the login form, and save this into a hidden input. The value is passed with the login credentials and added to the user's session, so it can be used for the duration of the session.

Jquery to add to login page only:

$('#istouch').val(1); // <-- value will be submitted with login form

if (window.addEventListener) {
    window.addEventListener('mousemove', function mouseMoveListener(){
        // Update hidden input value to false, and stop listening
        $('#istouch').val(0); 
        window.removeEventListener('mousemove', mouseMoveListener);
    });
} 

(+1 to @Dave Burt and +1 to @Martin Lantzsch on their answers)