window.addEventListener('touchstart', function onFirstTouch() {
// we could use a class
document.body.classList.add('user-is-touching');
// or set some global variable
window.USER_IS_TOUCHING = true;
// or set your app's state however you normally would
myFrameworkOfChoice.dispatchEvent('USER_IS_TOUCHING', true);
// we only need to know once that a human touched the screen, so we can stop listening now
window.removeEventListener('touchstart', onFirstTouch, false);
}, false);