TouchList.length

var numTouches = touchList.length;

target = document.getElementById("target");

target.addEventListener('touchstart', function(ev) {

  // If this touchstart event started on element target,
  // set touch to the first item in the targetTouches list;
  // otherwise set touch to the first item in the touches list
  var touch;

  if (ev.targetTouches.length >= 1)
     touch = ev.targetTouches.item(0);
  else
     touch = ev.touches.item(0);
}, false);