A detailed explanation of the environment variable process.env in Node.js

This article mainly introduces you to some things about the environment variable process.env in Node.js. The article introduces it in detail through sample code. It has certain reference learning value for everyone to learn or use node.js. Friends who need it Let’s learn together with the editor below.

Preface

In the past two days, I have been working on a deployment project with the operation and maintenance GG. One problem we encountered was a problem with our dev, uat, and product environments.

Because the front-end and back-end are separated, there will be the problem of switching the domain name of the back-end interface during the development and deployment process. After struggling all afternoon and searching various information, I figured out the Node environment variable process.env.

The following is a record of problem solving. Hope this helps someone who doesn't understand. Not much to say, let’s take a look at the detailed introduction.

Node environment variable

First of all, when we are developing single-page applications in react and vue, I believe that everyone is not familiar with process.env in the configuration file.

Can not remember? Black question mark.jpg.

These are the following things.

Literally, this is the env attribute. The configuration will be somewhat different in different environments of development and production.

Okay, let’s start to see what this so-called process is.

Document: http://nodejs.cn/api/process.html

Official explanation: The process object is a global (global variable) that provides relevant information and controls the current Node.js process . As an object, it is always available to Node.js applications, so there is no need to use require().

process (process) is actually a global variable that exists in nodejs.

Then, we can get some interesting things through this so-called process.

But today we mainly talk about process.env.

process.env

What is this?

Official: The process.env property returns an object containing user environment information.

Documentation: http://nodejs.cn/api/process.html#process_process_env

Oh, oh, it turns out that this attribute can return some information about the environment where the project is running.

What’s the use?

It's an obvious usage scenario, relying on this we can put a label on the server. In this case, we can do some configuration processing according to different environments. For example, turning on sourceMap, switching the domain name of the backend interface, etc.

你是 dev 环境
他是 uat 环境
她是 product 环境。

How to configure environment variables

The following describes how to configure environment variables for each environment.

Windows configuration

Temporary configuration

You can configure it directly in the cmd environment, view environment variables, add environment variables, and delete environment variables.

#node中常用的到的环境变量是NODE_ENV，首先查看是否存在 
set NODE_ENV 
#如果不存在则添加环境变量 
set NODE_ENV=production 
#环境变量追加值 set 变量名=%变量名%;变量内容 
set path=%path%;C:\web;C:\Tools 
#某些时候需要删除环境变量 
set NODE_ENV=

Permanent configuration

Right click (this computer) -> Properties (R) -> Advanced system settings -> Environment variables (N)...

Linux configuration

Temporary

View environment variables, add environment variables, delete environment variables

#node中常用的到的环境变量是NODE_ENV，首先查看是否存在
echo $NODE_ENV
#如果不存在则添加环境变量
export NODE_ENV=production
#环境变量追加值
export path=$path:/home/download:/usr/local/
#某些时候需要删除环境变量
unset NODE_ENV
#某些时候需要显示所有的环境变量
env

Permanent

Open the configuration file location

# 所有用户都生效
vim /etc/profile
# 当前用户生效
vim ~/.bash_profile

Add a statement similar to the following at the end of the file to set or modify environment variables

# 在文件末尾添加如下格式的环境变量
export path=$path:/home/download:/usr/local/
export NODE_ENV = product

After the final modification is completed, you need to run the following statement to reload the system

# 修改/etc/profile文件后
source /etc/profile
# 修改~/.bash_profile文件后
source ~/.bash_profile

Resolve the environment that causes the back-end interface Transformation problem

After figuring out this problem, we can set different NODE_ENV on machines in different environments. Of course, this field is not necessarily certain.
You can also change to other NODE_ENV_NIZUISHUAI, etc., it is customized anyway.

Solution steps

1. Modify the backend address configuration in the code

It is very simple, just use the process.env.NODE_ENV field to judge. (process is a global attribute of node, just use it directly)

2. Set the environment variable on linux

export NODE_ENV=dev

Then you can start happily The project is played.

At the end

Because my current project is React server-side rendering. Therefore, the backend request forwarding is not handed over to nginx for processing.
Like ordinary pure single-page applications, nginx is generally used to forward requests.

Related recommendations:

Better way to manage front-end environment variables

Share the steps on how to configure environment variables under Linux (picture )

Sharing the steps on how to configure environment variables under Linux (picture)

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