JavaScript: Function to detect if user agent is a "touch" device

gistfile1.js

<script>
    // Detect if user agent is on a "touch" device
    // http://stackoverflow.com/questions/4817029/whats-the-best-way-to-detect-a-touch-screen-device-using-javascript
    function isTouchDevice() {
      return !!('ontouchstart' in window) // works on most browsers
          || !!('onmsgesturechange' in window); // works on ie10
    }

    if (isTouchDevice()) {
        document.documentElement.className += ' touch';
    }
</script>