We tried the modernizr implementation, but detecting the touch events is not consistent anymore (IE 10 has touch events on windows desktop, IE 11 works, because the've dropped touch events and added pointer api).
So we decided to optimize the website as a touch site as long as we don't know what input type the user has. This is more reliable than any other solution.
Our researches say, that most desktop users move with their mouse over the screen before they click, so we can detect them and change the behaviour before they are able to click or hover anything.
This is a simplified version of our code:
var isTouch = true;
window.addEventListener('mousemove', function mouseMoveDetector() {
isTouch = false;
window.removeEventListener('mousemove', mouseMoveDetector);
});