我的index.js文件

import { getYear, getChineseMonth } from '../../../utils/helper'

Component({
  properties: {
    index: {
      type: Number,
      observer: function(newVal) {
        const val = newVal < 10 ? `0${newVal}` : newVal
        this.setData({
          _index: val
        })
      }
    }
  },

  data: {
    year: getYear(),
    month: getChineseMonth(),
    _index: 0
  }
})

老师的

Component({
  /**
   * 组件的属性列表
   */
  properties: {
    index:{
      type:String,
      observer:function(newVal, oldVal, changedPath){
        let val = newVal < 10?'0'+newVal:newVal
        this.setData({
          _index:val
        })
      }
    }
  },
  // wxs

  /**
   * 组件的初始数据
   */
  data: {
    months: [
      '一月', '二月', '三月', '四月', '五月', '六月', '七月', '八月', '九月', '十月', '十一月',
      '十二月'
    ],
    year: 0,
    month: '',
    _index:''
  },

  attached:function(){
    let date = new Date()
    let year = date.getFullYear()
    let month = date.getMonth()

    this.setData({
      year,
      month:this.data.months[month]
    })
  }
})