暴露配置到服务端和客户端

next/config模块使你应用运行时可以读取些存储在next.config.js的配置项。serverRuntimeConfig属性只在服务器端可用，publicRuntimeConfig属性在服务端和客户端可用。

// next.config.js
module.exports = {
  serverRuntimeConfig: { // Will only be available on the server side
    mySecret: 'secret'
  },
  publicRuntimeConfig: { // Will be available on both server and client
    staticFolder: '/static',
    mySecret: process.env.MY_SECRET // Pass through env variables
  }
}

// pages/index.js
import getConfig from 'next/config'
// Only holds serverRuntimeConfig and publicRuntimeConfig from next.config.js nothing else.
const {serverRuntimeConfig, publicRuntimeConfig} = getConfig()

console.log(serverRuntimeConfig.mySecret) // Will only be available on the server side
console.log(publicRuntimeConfig.staticFolder) // Will be available on both server and client

export default () => <div>
  <img src={`${publicRuntimeConfig.staticFolder}/logo.png`} alt="logo" />
</div>