移動端手指滑動距離

var startPosition={},deltaY,endPosition={};
document.addEventListener('touchstart',touch, false); 
document.addEventListener('touchmove',touch, false); 
document.addEventListener('touchend',touch, false); 
    
function touch (event){ 
    var event = event || window.event; 
    switch(event.type){ 
        case "touchstart": 
            var touch = event.touches[0];
            startPosition = {
                x: touch.pageX,
                y: touch.pageY
            }
            break; 
        case "touchend":
　　　　　　　break; 
        case "touchmove": 
            var touch = event.touches[0];
            endPosition = {
                x: touch.pageX,
                y: touch.pageY
            }
        deltaY = endPosition.y - startPosition.y;
　　　　　　　break; 
    } 
        
}