[Solved]-react evironment variables .env return undefined-Reactjs

FIX:

in babel.config.js, if you're using the optional configuration:

    {
  "plugins": [
    ["module:react-native-dotenv", {
      "moduleName": "@env",
      "path": ".env",
      "blacklist": null,
      "whitelist": null,
      "safe": false,
      "allowUndefined": true
    }]
  ]
}

you should then import:

import {API_URL, API_TOKEN} from "@env"

instead of:

import {API_URL, API_TOKEN} from "react-native-dotenv"

the NPM Package description itself has this inconsistency

DO NOT STORE OR USE API KEYS IN FRONTEND CODE SINCE IT IS EASILY READABLE THROUGH DEV TOOLS

Saving API keys in .env and using them in your React app will still be unsecured since the API key can be read from DevTools.

Use some simple backend code that will act as a proxy to your service.

Send required data through a request and then the backend should use that data including the API key stored on the backend, and then make a request to some particular service that needs that API key.

No need to prefix it with REACT_APP_, just identify your environment -

• if you are on development environment (npm start), you should be adding an environment variable in .env.development like - API_URL=http://example.com
• if you are on production environment, updating .env should work

Then use the same in your JS file as process.env.API_URL

Note: I've tested this on React JS v16.8

If you are using dev server on localhost know this that .env doesn't work here, you need to deploy website on "normal" server, it is a safety reason to not allow browser to see .env in staging

Also make sure that when you enter process.env.REACT_APP_YOURVARIABLE, your IDE don't add at the top of your file:

import process from "process";

This was my problem, I received undefined until I removed the accidentally added import

try by clearing the cache also.

npx react-native start --reset-cache

Solution:
1.Remove double quotation.("...").
2.Prefix Must be REACT_APP on every variable.

Right way:

REACT_APP_API_URL=http://localhost:8002

I hope its work.

In my case I started with naming the file process.env. As it happen and as the doc clearly states, the file should simply be named .env

Hey thanks guy what i did and worked was create a config.js file

 const dev={
    API_URL:"http://localhost:300"
}

const prod={
    API_URL:"llll"
}
const config=process.env.NODE_ENV=='development'?dev:prod
export default  config

Then i import wherever maybe in a component and get my data.

Another possible trap in which I fell was to define the variables not under the create-react-app folder but one above(where the Node server/backend .env is located). Make sure you don't do that because you will waste precious time, as I did today.

If the above solutions don't work for you then please check where is your ".env" file place. Like in my case everything I had done correctly but the mistake is I had placed the ".env" outside my project directory due to which I'm getting error.

Note: Your ".env" file should be in the same directory in which your "package.json" is.

1. restart the vscode (close the project, close the editor)
2. open it again
3. launch the project

In my case it help a lot. Also remember to start the name of your key with REACT_APP_YOUR_NAME_KEY

• Make sure you used the prefix REACT_APP on every variable

• Confirm that the variable names on the .env file match the ones on
  your js file.For example,REACT_APP_KEY in .env versus process.env.REACT_APP_KY

• If the development server was running, stop it then rerun using npm start it. I really struggled with this (variable is an undefined error).
• Every time you update the .env file, you need to stop the server and rerun it, as the environment variables are only updated during build (variable is an undefined error).
• Remove quotations from the values of the variables.

// Wrong: 
REACT_APP_KEY=”AHEHEHR”

// Right:
REACT_APP_KEY=AHEHEHR

when calling a .env variable from a JS file you need to call it by process.env. prefix before you write the .env variable

thus it would look like process.env.REACT_APP_NOT_SECRET_CODE

and do not forget to start your variable name by REACT_APP_ prefix as mentioned in previous answers, otherwise react will ignore it for security reasons.

• Add prefix REACT_APP_ on React environment variables.

  apiKey: process.env.REACT_APP_API_KEY
  

• Make sure .env file is in the root directory.

  src/
  .env
  .gitignore
  package.json
  package-lock.json
  

• Restart the development server after making changes in .env file.

• Copy only the value inside the quotation marks and don't forget to remove trailing commas(It haunted me for several hours). These examples will give you an error.

  REACT_APP_API_KEY=Ach2o1invVocSn25FcQhash209,
  REACT_APP_API_KEY="Ach2o1invVocSn25FcQhash209",
  REACT_APP_API_KEY="Ach2o1invVocSn25FcQhash209"
  

You will probably need to call dotenv.config() as suggested by the document

If you are using create-react-app, you don't need dotenv package. You will need to add REACT_APP_ prefix to the variable name in .env file. See the document here

Three things to note here

1. the variable should be prefixed with REACT_APP_

   eg: REACT_APP_WEBSITE_NAME=hello

2. You need to restart the server to reflect the changes.

3. Make sure you have the .env file in your root folder(same place where you have your package.json) and NOT in your src folder.

After that you can access the variable like this process.env.REACT_APP_SOME_VARIABLE

Additional tips

1. No need to wrap your variable value in single or double quotes.
2. Do not put semicolon ; or comma , at the end of each line.

Read more here(my own post) and the official docs