code: function resetPosAndIdx (curIndex, totalNum, deviceWidth, endPos) {
    let endInfo = {
      endPos: 0,
      endIndex: curIndex
    }
    if (curIndex === totalNum - 1) {
      endInfo.endPos = -deviceWidth
      endInfo.endIndex = 1
    } else if (curIndex === 0) {
      // if it is last one
      endInfo.endPos = -(totalNum - 2) * deviceWidth
      endInfo.endIndex = totalNum - 2
    } else {
      endInfo.endPos = endPos
    }
    return endInfo
  }
docs: 计算滚动之后需要到达的坐标 resetPosAndIdx
  
  @param {number} curIndex curIndex
  @param {number} totalNum totalNum
  @param {number} deviceWidth deviceWidth
  @param {number} endPos endPos
  @return {Object}