code: function getNativeScrollbarWidth() {
      var container = document.body;
  
      var box = document.createElement("div");
      var cev = document.createElement("div");
  
      box.className = HideNativeBarClass;
      box.style.position = "absolute";
      box.style.pointerEvents = "none";
      box.style.bottom = "0";
      box.style.right = "0";
      box.style.width = "100px";
      box.style.height = "100px";
      box.style.overflow = "hidden";
  
      cev.style.width = "100%";
      cev.style.height = "100%";
  
      box.appendChild(cev);
      container.appendChild(box);
  
      var fullWidth = cev.offsetWidth;
      var fullHeight = cev.offsetHeight;
  
      box.style.overflow = "scroll";
  
      var v = fullWidth - cev.offsetWidth;
      var h = fullHeight - cev.offsetHeight;
  
      container.removeChild(box);
  
      return {
          v: v,
          h: h
      };
  }
docs: 计算原生圆滚动条大小
  @returns {Array}  [v, h]