Note: this feature is available with [email protected] and higher.

Your project can consume variables declared in your environment as if they were declared locally in your JS files. By default you will have NODE_ENV defined for you, and any other environment variables starting with REACT_APP_.

WARNING: Do not store any secrets (such as private API keys) in your React app!

Creating a Portable Python Environment This walkthrough will demonstrate a method to copy an exact environment on one machine and transfer it to a another machine. We'll start by collecting the package requirements of a given set of python files, create an environment based on those requirements, then export it as a tarball for distribution on. Here you will learn node js.env file example. This article will give you simple example of node js environment configuration file. In this simple example we will create.env file for environment configuration variable like port, app name, database configuration etc. We will use dotenv npm package for setup.env file variable.

The file option is interesting because it means you can also create an environment variable to launch a program. For example, you can point an environment variable to any EXE file on your system. When you invoke the variable, it will launch the program. Select Advanced system settings. In the Advanced tab, select Environment Variables. You will now be able to enter the environmental variable. Most environmental variables are given to you in the form 'Variablename=Variablevalue'. You can't make.env files anymore, you'll have to use this new GUI by clicking the lock icon in the sidebar (near where the files are kept). Then you just enter the name of a key and its value. Then you just enter the name of a key and its value.

Environment variables are embedded into the build, meaning anyone can view them by inspecting your app's files.

The environment variables are embedded during the build time. Since Create React App produces a static HTML/CSS/JS bundle, it can’t possibly read them at runtime. To read them at runtime, you would need to load HTML into memory on the server and replace placeholders in runtime, as described here. Alternatively you can rebuild the app on the server anytime you change them.

Note: You must create custom environment variables beginning with REACT_APP_. Any other variables except NODE_ENV will be ignored to avoid accidentally exposing a private key on the machine that could have the same name. Changing any environment variables will require you to restart the development server if it is running.

These environment variables will be defined for you on process.env. For example, having an environment variable named REACT_APP_NOT_SECRET_CODE will be exposed in your JS as process.env.REACT_APP_NOT_SECRET_CODE.

There is also a built-in environment variable called NODE_ENV. You can read it from process.env.NODE_ENV. When you run npm start, it is always equal to 'development', when you run npm test it is always equal to 'test', and when you run npm run build to make a production bundle, it is always equal to 'production'. You cannot override NODE_ENV manually. This prevents developers from accidentally deploying a slow development build to production.

These environment variables can be useful for displaying information conditionally based on where the project is deployed or consuming sensitive data that lives outside of version control.

First, you need to have environment variables defined. For example, let’s say you wanted to consume an environment variable inside a <form>:

During the build, process.env.REACT_APP_NOT_SECRET_CODE will be replaced with the current value of the REACT_APP_NOT_SECRET_CODE environment variable. Remember that the NODE_ENV variable will be set for you automatically.

When you load the app in the browser and inspect the <input>, you will see its value set to abcdef, and the bold text will show the environment provided when using npm start:

The above form is looking for a variable called REACT_APP_NOT_SECRET_CODE from the environment. In order to consume this value, we need to have it defined in the environment. This can be done using two ways: either in your shell or in a .env file. Both of these ways are described in the next few sections.

Having access to the NODE_ENV is also useful for performing actions conditionally:

When you compile the app with npm run build, the minification step will strip out this condition, and the resulting bundle will be smaller.

Referencing Environment Variables in the HTML#

Note: this feature is available with [email protected] and higher.

You can also access the environment variables starting with REACT_APP_ in the public/index.html. For example:

Note that the caveats from the above section apply:

• Apart from a few built-in variables (NODE_ENV and PUBLIC_URL), variable names must start with REACT_APP_ to work.
• The environment variables are injected at build time. If you need to inject them at runtime, follow this approach instead.

Adding Temporary Environment Variables In Your Shell#

Defining environment variables can vary between OSes. It’s also important to know that this manner is temporary for the life of the shell session.

Windows (cmd.exe)#

(Note: Quotes around the variable assignment are required to avoid a trailing whitespace.)

Windows (Powershell)#

Linux, macOS (Bash)#

Adding Development Environment Variables In .env#

Note: this feature is available with [email protected] and higher.

To define permanent environment variables, create a file called .env in the root of your project:

Note: You must create custom environment variables beginning with REACT_APP_. Any other variables except NODE_ENV will be ignored to avoid accidentally exposing a private key on the machine that could have the same name. Changing any environment variables will require you to restart the development server if it is running.

Note: You need to restart the development server after changing .env files.

.env files should be checked into source control (with the exclusion of .env*.local).

What other .env files can be used?#

Note: this feature is available with [email protected] and higher.

• .env: Default.
• .env.local: Local overrides. This file is loaded for all environments except test.
• .env.development, .env.test, .env.production: Environment-specific settings.
• .env.development.local, .env.test.local, .env.production.local: Local overrides of environment-specific settings.

Files on the left have more priority than files on the right:

• npm start: .env.development.local, .env.local, .env.development, .env
• npm run build: .env.production.local, .env.local, .env.production, .env
• npm test: .env.test.local, .env.test, .env (note .env.local is missing)

These variables will act as the defaults if the machine does not explicitly set them.

Please refer to the dotenv documentation for more details.

Note: If you are defining environment variables for development, your CI and/or hosting platform will most likely needthese defined as well. Consult their documentation how to do this. For example, see the documentation for Travis CI or Heroku.

Expanding Environment Variables In .env#

Note: this feature is available with [email protected] and higher.

Expand variables already on your machine for use in your .env file (using dotenv-expand).

For example, to get the environment variable npm_package_version:

Or expand variables local to the current .env file:

by Erisan Olasheni

Have you ever found yourself in a situation where you needed custom environment variables for different development stages of your app? Here is a one-line solution.

Development has been much easier since the invention of the .env file. You can easily set your environment variables and values with the syntax ENV_VARIABLE=VALUE and boom! These variables got loaded as your environment variables, making it possible to get quick access to them:

In case you are still wondering what all this means, well, you are probably new to the .env file. It’s actually a simple configuration text file that is used to define some variables you want to pass into your application’s environment.

This file needs a something like a parser to make it work. The parser reads the variable definitions one-by-one and parses them to the environment. It uses the format ENV_VARIABLE=VALUE (in the case of Node.js: process.env[ENV_VARIABLE]=VALUE).

Of course, this is not a built-in feature in Node.js. You have to engineer it with a popular module called dotenv.

It’s a nice workaround, as it has really made development easier between co-developers and across the dev community as a whole. I personally had been using the dotenv module, until I got stranded trying to get a solution that could make me use a different configuration file for a particular environment. That would be even cooler…right? Yes! But unfortunately, the dotenvmodule doesn’t provide us with this goody.

So what’s next? We need this thing to make development and testing easier across different development stages!

How about custom .env files for different environment stages?

Don’t you think that would be a good solution? Defining custom environment variables by just creating a .env.envname file? Cool! That is what custom-env has come to do.

Custom env is a library built to make development easier by allowing multiple .env configuration for different environments. This is done by loading environment variables from a .env.envname file into the node’s process.env object.

Installation

Just grab it with the following command:

Usage

By default, custom-env picks the .env file for your dev stage. However, to customize for a different stage, add the name as a suffix as in .env.envname.

Example

We can define a custom environment variable for a staging development.

• Create a .env.staging file
• Define your variables

• Access your variables

Expected Output

That’s it, pretty easy. Feel free to define more variables for different stages you think you have, like:

.env.testing, .env.staging, .env.server1, .env.server2, .env.localhost

Set to the Current Environment

You can tell custom-env to use a configuration that matches your current development stage by passing trueto the env()method.

Create .env File Linux

Example

File: index.js

Now let’s define a staging configuration file:

File: .env.staging

Now let’s serve node with the staging environment:

Expected Output

Activate Conda Environment In Powershell

There you go!

Create .env File React

Full Documentation

For the full documentation of custom-env, visit the npm pagehttps://www.npmjs.com/package/custom-env

Source Code

You can get or contribute to the custom-envsource code at https://github.com/erisanolasheni/custom-env

Happy Coding!