阻止手机端手指触摸事件（单指）

var obj = document.getElementById('pDiv');
        obj.addEventListener('touchmove', function(event) {
             // if finger one touched
            if (event.targetTouches.length == 1) {
                event.preventDefault();// preventDefault 
                var touch = event.targetTouches[0];
                // let obj move to finger's postion
                obj.style.left = touch.pageX-50 + 'px';
                obj.style.top = touch.pageY-50 + 'px';
                }
        }, false);