Mastering React Environment Variables: Say Goodbye to `Undefined` Errors (with Examples)

Table of content

  1. Introduction
  2. What are Environment Variables?
  3. Why Use Environment Variables in React?
  4. Setting Up Environment Variables in React
  5. Using Environment Variables in your React Components
  6. Example #1: Displaying the API Key
  7. Example #2: Configuring Different Environments
  8. Conclusion


Have you ever heard of the phrase "less is more"? It may seem counterintuitive in our "more is better" society, but when it comes to productivity, it may be the key to success. In fact, many famous figures have emphasized the importance of doing less in order to achieve more. For example, Albert Einstein once said, "If you want to be more productive, then start by deleting unnecessary tasks from your to-do list."

In this article, we'll explore the concept of doing less and how it can be applied to increase productivity in your work with React environment variables. We will provide examples and step-by-step instructions for mastering React environment variables to avoid those pesky "undefined" errors that can slow you down.

So, let's challenge the common notion of productivity and consider adopting a "less is more" approach. By doing less and focusing on what truly matters, we can optimize our productivity and achieve greater success in our projects and goals.

What are Environment Variables?

Environment variables are a powerful tool that can be used to define and manage settings specific to an environment. Simply put, environment variables are system-wide variables that contain information about the environment in which they are being used. They are used to define configuration settings, such as API keys, database connections and other settings specific to an environment.

Many developers struggle with managing environment variables, particularly in large projects. Undefined errors frequently arise when a variable has not been defined or if it has been incorrectly defined. This can lead to hours of frustration and wasted time. However, mastering environment variables can help to eliminate these errors and increase productivity.

One of the biggest advantages of using environment variables is the ability to manage configuration settings across different environments, such as development, staging, and production. Using environment variables to define these settings makes it easy to keep the settings consistent and ensure that they are always up to date. Additionally, environment variables can be more secure than hardcoding sensitive information, such as usernames and passwords, into code or configuration files.

In short, environment variables are an essential tool for developers who want to efficiently manage their application settings, ensure consistent environments across development, staging, and production, and use safer methods to manage sensitive information.

Why Use Environment Variables in React?

You import your components, stylesheets, and other dependencies with ease. But what about environment variables? Are you still hard-coding API keys and other sensitive data into your code? Are you tired of seeing "Undefined" errors pop up on your screen? It's time to master environment variables in React.

Why use environment variables? They allow you to store sensitive data, such as API keys and passwords, outside of your codebase. This adds an extra layer of security, as anyone who gains access to your code won't be able to see these sensitive values. Environment variables also make it easy to switch between different environments, such as development and production, because you can specify different values for each environment.

In the words of John Allspaw, former CTO of Etsy, "The difference between configuration and code is that configuration changes more frequently." With environment variables, you can change your configuration without changing your code. This is especially useful in a team setting, where multiple developers may be working on the same codebase but have different configurations.

In summary, using environment variables in React makes your code more secure and flexible. It's a best practice that you should adopt if you haven't already. So say goodbye to "Undefined" errors and hello to a more professional and robust codebase.

Setting Up Environment Variables in React

is a crucial step that developers often overlook. Environment variables are the key-value pairs that help you store sensitive information like API keys, database URLs, and other configuration details. This makes them a vital part of any application that needs to interact with the outside world.

The good news is that is relatively straightforward. One way to do it is by using the dotenv package. dotenv is a zero-dependency package that loads environment variables from a .env file and makes them available in your application via process.env.

To use dotenv in your React application, install it as a dev-dependency using npm:

npm install dotenv --save-dev

Next, create a .env file at the root of your project and add your variables as follows:


Note that variables starting with REACT_APP_ are automatically made available in your React application. You can then access them via process.env:


By setting up your environment variables this way, you can easily manage sensitive information across different environments without worrying about exposing them to prying eyes.

As famed computer scientist Alan Perlis once said, "Fools ignore complexity. Pragmatists suffer it. Some can avoid it. Geniuses remove it." By setting up environment variables in your React application, you can remove unnecessary complexity and streamline your development process. Don't be a fool or a pragmatist when it comes to productivity – be a genius and simplify your life.

Using Environment Variables in your React Components

Are you tired of constantly dealing with 'undefined' errors in your React components? It's time to start using environment variables.

Environment variables allow you to set global variables that can be accessed throughout your React app. This means you can set and change values for things like API keys, database URLs, and other configurations without having to hardcode them into your code.

is easy. Simply create a .env file in the root of your project and add your variables in the format of REACT_APP_VAR_NAME=value. Then, in your component, you can access the value using process.env.REACT_APP_VAR_NAME.

Not only does using environment variables make your code more organized and easier to manage, it also adds a layer of security by keeping sensitive information out of your codebase.

So why haven't you been using environment variables all along? It's time to say goodbye to those 'undefined' errors and start implementing this useful tool in your React projects. As the famous tech entrepreneur Elon Musk once said, "I think it's very important to have a feedback loop, where you're constantly thinking about what you've done and how you could be doing it better." By adopting new practices like using environment variables, we can constantly improve our code and become more productive developers.

Example #1: Displaying the API Key

In our first example, we'll be displaying an API key in a React app. Many developers make the mistake of hardcoding the API key directly into their codebase. This is a bad practice because it exposes the key to anyone who has access to the code. Plus, if the key needs to be changed, developers would have to manually update it in every relevant file.

Instead, let's use environment variables to store our API key. First, we'll create a new file called ".env.local" in the root of our project. In this file, we'll define our API key as "REACT_APP_API_KEY=insert_your_key_here". Note that the variable name must start with "REACT_APP_" for it to be recognized by Create React App.

Next, we can access the API key from our code by using "process.env.REACT_APP_API_KEY". For example, if we wanted to use the API key in our fetch request, we could do something like:

  .then(response => response.json())
  .then(data => console.log(data))

This way, we can keep our API key secure and easily change it if needed. Plus, we don't have to worry about accidentally committing it to our code repository.

As Albert Einstein once said, "It's not that I'm so smart, it's just that I stay with problems longer." By taking the time to master React environment variables, we can avoid common pitfalls and become better developers in the process. So let's say goodbye to those pesky "undefined" errors and hello to a more productive workflow!

Example #2: Configuring Different Environments

Another use case for environment variables in React is configuring different environments. As your application grows, you might need to have different settings and configurations for different environments. For example, you might have different API endpoints for development, testing, and production environments.

Instead of hardcoding these values in your code, you can use environment variables to configure them. This makes it easier to manage and deploy your application in different environments without having to modify your code. Plus, it reduces the risk of accidentally deploying the wrong configuration.

To set up different environments, you can create environment-specific configuration files, such as .env.development, .env.test, and .env.production. These files can contain different values for the same environment variables.

For example, in your development environment, you might have the following settings:


While in your production environment, you might have the following settings:


To use these settings in your React application, you can import them using process.env.REACT_APP_{VARIABLE_NAME} syntax. For example:

const apiUrl = process.env.REACT_APP_API_URL;
const isDebug = process.env.REACT_APP_DEBUG === 'true';

  .then(response => {
    if (isDebug) {
    return response.json();
  .then(data => console.log(data));

Using environment variables for configuring different environments not only makes it easier to manage configuration but also reduces the risk of errors and improves security. By separating configuration from code, you can make your application more flexible, scalable, and maintainable.


In , mastering React environment variables is a crucial skill for React developers to prevent any undefined errors in their code. With the help of these environment variables, developers can easily manage different configurations, settings, and secrets across various hosting environments. Moreover, it saves a lot of time and effort in debugging, as developers can quickly switch between their local or staging environment without hard coding the values in their codebase.

So, if you are a React developer or planning to start with React, it's essential to learn how to use the environment variables in your projects effectively. The examples and best practices discussed in this article will help you get started and optimize your React application for different environments.

To quote the famous phrase by Bruce Lee, "It's not the daily increase but the daily decrease. Hack away at the unessential." In the context of productivity, it's essential to take a step back and evaluate the tasks that are truly necessary and eliminate the ones that are not. By doing less, we can focus more on the crucial tasks and produce better results. It's time to rethink our approach to productivity and embrace the power of doing less.

As an experienced Senior Software Engineer, I have a proven track record of success in the hospital and healthcare industry as well as the telecom industry. With a strong skill set in JAVA, LINUX, and SPRING, I am well-equipped to handle complex software engineering challenges. My passion for software engineering started early, and I pursued a Bachelor of Engineering degree in Computer Science from Chitkara University. Throughout my academic and professional career, I have honed my skills in software development, including application design, coding, testing, and deployment. In addition to my technical expertise, I am a strong communicator and collaborator. I believe in working closely with my team members and clients to ensure that all project goals are met efficiently and effectively.
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