How to detect production or development build at runtime in React

This is a short tutorial about how to check whether to react application is a production build or development code at runtime.

Sometimes, We want to check whether to react code is in production mode or not

In React, We have two modes of builds

  • production is a minified version of javascript and HTML code and rendered on browser client machine and performance is good
  • development - javascript and HTML code is not minified and loads immediately.

Both these builds have different environment variables to hold related to build code.

How to check production or development mode with create-react-app

create-react-app is a react cli tool to generate an application from scratch with a folder structure. It also includes dependencies and builds pipelines configured with a webpack of development and production build.

We have node environment variables process.env.NODE_ENV defined with an application created with the create-react-app tool. It checks the environment of your application running and returns development of code running development mode.

  • process.env.NODE_ENV = development is for development build
  • process.env.NODE_ENV != development is for production build

In code, we can check at run time using

if (!process.env.NODE_ENV || process.env.NODE_ENV === "development") {
  // development build code
} else {
  // production build code

Check your react native is production or development build

In React Native, the global environment variable DEV is available to use.

It is a javascript environment variable that we can use to set to true for development and false for production.

if (__DEV__) {
  console.log("Development code build");
} else {
  console.log("Production code build");

This is why we can check to react native is using development or production build.