nuxt框架 使用asyncData，每次有改动都需要重新npm run dev才会正常显示

Question

nuxt框架 使用asyncData，每次有改动都需要重新npm run dev才会正常显示 。否则会报错，代码和报错如下

  asyncData({ params }) {
    let getNews = axios.getNews({ limit: 2 })
    let getBannerPic = axios.getBannerPic()
    let promise = Promise.all([getNews, getBannerPic])
    return promise.then(res => {
      let banners = []
      let bannersData = res[1].data.data
      for (let i = 0; i < bannersData.length; i++) {
        banners.push(bannersData[i]['mobile_img']['url'])
      }
      console.log(banners)
      return {
        news: res[0].data,
        banners: banners
      }
    })
  }

报错
Cannot read property 'length' of undefined 19:37:13

at promise.then.res (pages_index.js:790:39)
at process._tickCallback (internal/process/next_tick.js:68:7)

但是每次 执行npm run dev又是正常的，改其他的东西的时候 会自动编译 这里就就会报错