js按钮浮动随手指方向移动而移动

window.document.getElementById("moveDIV").addEventListener("touchmove", function (event) {
            
            event.preventDefault();
            
            if (event.targetTouches.length == 1) {
                var touch = event.targetTouches[0];  // 把元素放在手指所在的位置
             
                if(touch.pageX + $("#moveDIV").width() > $(window).innerWidth()){
                    
                     window.document.getElementById("moveDIV").style.left = ($(window).innerWidth() - $("#moveDIV").width()) + 'px';
                    
                }else if(touch.pageX < $("#moveDIV").width()){
                    
                    window.document.getElementById("moveDIV").style.left = 0 + 'px';
                    
                }else{
                    
                    window.document.getElementById("moveDIV").style.left = touch.pageX + 'px';
                }
                
               if(touch.pageY + $("#moveDIV").height() > $(window).innerHeight()){
                   
                       window.document.getElementById("moveDIV").style.top = ($(window).innerHeight() - $("#moveDIV").height())+ 'px';
                       
               }else if(touch.pageY < $("#moveDIV").height()){
                    
                    window.document.getElementById("moveDIV").style.top = 0 + 'px';
                    
                }else {
                   
                       window.document.getElementById("moveDIV").style.top = touch.pageY + 'px';
                       
               }
            }
        },false)