【実録】Nuxt.jsの既存プロジェクトを一足早くNuxt v2へとアップグレードする方法 ref: https://qiita.com/potato4d/items/7b3119c88869d7622a7d

auth.js

export default async function(context) {
-  const { app, store, route, redirect, isServer, req } = context
+  const { app, store, route, redirect, req } = context
-  if (isServer) {
+  if (process.server) {
    // 認証の処理
  } else {
    // クライアントでの処理
  }
  // ...
}

axios.js

export default function ({ $axios, store }) {
  $axios.onRequest((config) => {
    if (store.state.token) {
      config.headers.common['Authorization'] = store.state.token
    }
    return config
  })
}

file1.txt

[potato4d@snowcat sequeue-web (master)] $ yarn remove nuxt @nuxtjs/axios
yarn remove v1.6.0
[1/3] 🗑  Removing module nuxt...
[2/3] 🗑  Removing module @nuxtjs/axios...
[3/3] 📃  Regenerating lockfile and installing missing dependencies...
success Uninstalled packages.
✨  Done in 11.43s.

file2.txt

[potato4d@snowcat sequeue-web (master)]$ yarn add nuxt-edge @nuxtjs/axios
yarn add v1.6.0
[1/4] 🔍  Resolving packages...
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
[4/4] 📃  Building fresh packages...
success Saved lockfile.
success Saved 527 new dependencies.

file7.txt

クライアントビルド：
Version: webpack 3.10.0
Time: 22505ms

サーバーバンドルの作成:
Version: webpack 3.10.0
Time: 4903ms

file8.txt

クライアントビルド:
Version: webpack 4.7.0
Time: 19148ms
Built at: 2018-05-07 21:08:09

サーバーバンドルの作成:
Version: webpack 4.7.0
Time: 4491ms
Built at: 2018-05-07 21:08:14

nuxt.config.js

{
  // ...
  axios: {
    credentials: false,
    baseURL: process.env.NODE_ENV == 'production' ? 'https://~~~~~~~~~~~~~' : 'http://localhost:8000',
    requestInterceptor: (config, { store }) => {
      if (store.state.token) {
        config.headers.common['Authorization'] = store.state.token
      }
      return config
    }
  },
  // ...
}

package.json

{
  ...
  "dependencies": {
    "@nuxtjs/axios": "^5.3.1",
    "@nuxtjs/toast": "^3.0.1",
    "@potato4d/jpy": "^0.0.1",
    "cookie": "^0.3.1",
    "delay": "^2.0.0",
    "js-cookie": "^2.2.0",
    "lodash": "^4.17.4",
    "nuxt-edge": "^2.0.0-25425967.7d92486"
  },
  ...
}