code: function indicatorDot (domId) {
        let indicDom = document.getElementById(domId)
        if (!indicDom) {
          return
        }
        dotItems = indicDom.children
        let dotLen = dotItems.length
  
        if (index) {
          // 清除DOM中预先设置的mip-carousel-activeitem类
          dotItems = Array.prototype.slice.call(dotItems)
          dotItems.forEach(dotItem => {
            removeClass(dotItem, carouselParas.activeitem)
          })
          addClass(dotItems[imgIndex - 1], carouselParas.activeitem)
        }
  
        if (dotLen === childNum - 2) {
          for (let i = 0; i < dotLen; i++) {
            dotItems[i].count = i
            dotItems[i].addEventListener('click', function (event) {
              let count = this.count
              clearInterval(moveInterval)
              move(wrapBox, imgIndex, count + 1)
              if (isAutoPlay) {
                autoPlay()
              }
            })
          }
        } else {
          // 若个数不匹配，则隐藏掉indicator
          addClass(indicDom, 'mip-hide')
          dotItems = []
        }
      }
docs: 处理圆点型指示器