Poptip插件拖动造成IOS下与同页面下mescroll.js也被拖动的解决，即对e.preventDefault();的理解

//增加第3行到第5行代码

down() {
  this.flags = true;
  document.body.addEventListener('touchmove', function (e) {
    e.preventDefault();
  }, {passive: false});
  var touch;
  if (event.touches) {
    touch = event.touches[0];
  } else {
    touch = event;
  }
  this.position.x = touch.clientX;
  this.position.y = touch.clientY;
  this.dx = moveDiv.offsetLeft;
  this.dy = moveDiv.offsetTop;
},

//向下拖动Poptip后需要还原浏览器的"拖动事件"监听,参考第5行-7行代码

// 鼠标释放时候的函数
end() {
  window.localStorage.setItem('position', JSON.stringify({x: this.xPum, y: this.yPum}));
  this.flags = false;
  document.body.addEventListener('touchmove', function (e) {
    window.event.returnValue = true;
  });
},