[Nuxt.js] Firebaseの設定で環境変数dotenvを扱う

$ npm i --save @nuxtjs/dotenv
$ yarn add @nuxtjs/dotenv

nuxt.config.js

  plugins: [
    '~/plugins/firebase.js',
  ],
  modules: [
    '@nuxtjs/dotenv',
  ],

plugins/firebase.js

import firebase from "firebase/app";
import "firebase/auth";

if (!firebase.apps.length) {
  firebase.initializeApp({
    apiKey: process.env.API_KEY,
    authDomain: process.env.AUTH_DOMAIN,
    databaseURL: process.env.DATABASE_URL,
    projectId: process.env.PROJECT_ID,
    storageBucket: process.env.STORAGE_BUCKET,
    messagingSenderId: process.env.MESSAGING_SENDER_ID,
    appId: process.env.APP_ID
  })
}

export default firebase;

.envファイル

API_KEY='AIXXXXXXXXXXXXXXXXXXXXXXXX'
AUTH_DOMAIN='hogefuga.firebaseapp.com'
DATABASE_URL='https://hogefuga.firebaseio.com'
PROJECT_ID='hogefugao'
STORAGE_BUCKET='hogefuga.appspot.com'
MESSAGING_SENDER_ID='123456789'
APP_ID='1:123456789:web:abcde1234'

参考

• nuxt-community/dotenv-module