Next.js pass NODE_ENV to client
I’m building a React SSR App, using Next.js.
I want to be able to access the NODE_ENV on the client side, as this will tell my app which API endpoints to use.
I’m struggling to find a decent approach for this. I’d like to define the NODE_ENV as a window variable when I first render the page on the server, and then in my helper function where I make the API call, I would check if the code is being called on the server or the client, and using the window or process.env objects as required.
Does anyone have a good solution for such a problem? It must be a common issue but I can’t find any good solutions.
1. You can include it in webpack configuration (using dotenv-webpack dependency):
require('dotenv').config()
const path = require('path')
const Dotenv = require('dotenv-webpack')
module.exports = {
webpack: (config) => {
config.plugins = config.plugins || []
config.plugins = [
...config.plugins,
// Read the .env file
new Dotenv({
path: path.join(__dirname, '.env'),
systemvars: true
})
]
return config
}
}Reference: here
2. using babel plugin to import the variable towards the entire app:
env-config.js
const prod = process.env.NODE_ENV === 'production'
module.exports = {
'process.env.BACKEND_URL': prod ? 'https://api.example.com' : 'https://localhost:8080'
}
.babelrc.js
const env = require('./env-config.js')
module.exports = {
presets: ['next/babel'],
plugins: [['transform-define', env]]
}
index.js
export default () => (
<div>Loading data from { process.env.BACKEND_URL }</div>
)
Reference: here
3. Using next/config:
next.config.js
module.exports = {
publicRuntimeConfig: {
API_URL: process.env.API_URL
}
}
index.js
import React from 'react'
import getConfig from 'next/config'
const {publicRuntimeConfig} = getConfig()
const {API_URL} = publicRuntimeConfig
export default class extends React.Component {
static async getInitialProps () {
// fetch(`${API_URL}/some-path`)
return {}
}
render () {
return <div>
The API_URL is {API_URL}
</div>
}
}
Reference: here
Using Next’s build-time configuration
@DarrylR already mentioned using next.config.js and
Next’s runtime configuration,
but you can also use Next’s build-time configuration.
This lets you put the process.env.XXXX right into the code (as shown in step 3 below), and you don’t have to import anything. However, if you env variables should be set both when you build locally with Next.js and when you deploy to ZEIT Now, I don’t know if you can keep them in just one file using this method (see step 2 below).
The runtime configuration docs suggest you normally want to use build-time configuration:
Warning: Generally you want to use build-time configuration to provide your configuration. The reason for this is that runtime configuration adds rendering / initialization overhead and is incompatible with automatic prerendering.
Steps:
1. Set NODE_ENV for build process
1.1 Using ZEIT Now
If you deploy using ZEIT Now, you can set the env variables used at build time in now.json:
{
"version": 2,
"build": {
"env": {
"NODE_ENV": "production"
}
}
}
1.2 When running locally (optional)
If you want NODE_ENV to be set when running locally as well, this will not be set by now.json.
However you can set it in other ways, such as:
$ NODE_ENV=production npm run build
or change the build script in package.json to
"build": "NODE_ENV=production next build"
You can of course also set NODE_ENV for other scripts than build if you want that.
2. Make Next inline value of process.env.NODE_ENV
Add this to the next.config.js as described here:
module.exports = {
env: {
NODE_ENV: process.env.NODE_ENV
}
};
3. Use in code
if (process.env.NODE_ENV === "production") {
console.log("In production")
} else {
console.log("Not in production")
}
Another Easy solution:
create 2 files on root folder:
.env.development
.env.production
inside add variables as you need, for example in .env.development file:
NEXT_PUBLIC_ENV="development"
and in .env.production file:
NEXT_PUBLIC_ENV="production"
Then use it for example:
console.log('Version: ', process.env.NEXT_PUBLIC_ENV);
Since Next.js 9.4, NextJs has now built-in support for environment variables, which allows you to do the following using .env files:
An example .env.local:
DB_HOST=localhost
DB_USER=myuser
DB_PASS=mypassword
If you want to expose the env variables to the client, you have to prefix the variable with NEXT_PUBLIC_ for example:
NEXT_PUBLIC_API_PORT=4000
If you want to use the variable, you can use it like this: process.env.NEXT_PUBLIC_API_PORT
For the documentation see here
