docs: function (vnode, callback) {
      const info = { result: false }
  
      if (vnode && vnode === 'viewport') {
        info.result = true
        info.size = {
          width: document.documentElement.clientWidth,
          height: document.documentElement.clientHeight,
          top: 0,
          left: 0,
          right: document.documentElement.clientWidth,
          bottom: document.documentElement.clientHeight
        }
      }
      else if (vnode && vnode.$el) {
        info.result = true
        info.size = vnode.$el.getBoundingClientRect()
      }
  
      const message = info.result ? info : {
        result: false,
        errMsg: 'Illegal parameter'
      }
  
      callback && callback(message)
      return message
    }