输出的结果是没有任何问题的，但是浏览器就是会报这个错误
<template>
<div>
<ul v-if="data.length>0">
        <li v-for="item in data" :key="item.id">
          <div class="foot_title" v-html="dateFormat(item.time)"></div>
          <div class="foot_list" v-for="list in item.commodityList" :key="list.id">
              <div class="foot_desc">
                  <div>{{list.productName}}</div>
              </div>
          </div>
        </li>
      </ul>
      <div v-else class="no-collect">
        <p>暂无浏览历史~</p>
      </div>
</div>

js部分：data () {
    return {
      data: [
        {time: '07/16',
          commodityList: [
            {productName: '苹果'},
            {productName: '苹果'}
          ]
        },
        {time: '07/13',
          commodityList: [
            {productName: '雪梨'},
            {productName: '雪梨'}
          ]
        },
        {time: '07/12',
          commodityList: [
            {productName: '西瓜'},
            {productName: '西瓜'}
          ]
        }
      ],
      titleText: '今天'
    }
  },
 methods: {
    dateFormat  (val = '') {
      let myDate = new Date() // 获取系统当前时间
      let day1 = new Date(val)
      let day2 = new Date(myDate.getMonth() + 1 + '/' + myDate.getDate())
      const number = (day2 - day1) / (1000 * 60 * 60 * 24)
      if (number === 0) { //问题出在这里！！！
        this.titleText = '今天'
      } else if (number === 1) {
        this.titleText = '昨天'
      } else {
        this.titleText = val
        console.log(number)
      }
      return this.titleText
    }
  }