Resolving the 'React must be in scope when using JSX' Error

Summary: Learn how to resolve the "React must be in scope when using JSX" error in your React app by understanding why it occurs and how to implement a solution effectively.
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Resolving the React must be in scope when using JSX Error

Encountering the "React must be in scope when using JSX" error in your React application can be perplexing, especially if you're new to the library. This issue arises due to the way JSX transforms into JavaScript. Let's demystify this error and explore how to resolve it.

Why Does This Error Occur?

Whenever you write JSX, such as:

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[[See Video to Reveal this Text or Code Snippet]]

For the transformed code to work, React must be in the scope of your file. If it isn't, you'll encounter the error: React must be in scope when using JSX.

How to Resolve the Error

Import React in Your File

The simplest solution is to ensure React is imported in any file that uses JSX:

[[See Video to Reveal this Text or Code Snippet]]

This step ensures that the React object is available in the scope, allowing the JSX transformation process to work correctly.

Automatically Use React’s New JSX Transform (React 17+)

With the release of React 17, a new JSX Transform was introduced that does not require importing React in every file. If you’re using React 17 (or higher) and a modern setup with Babel, you can leverage this feature:

[[See Video to Reveal this Text or Code Snippet]]

[[See Video to Reveal this Text or Code Snippet]]

With this setup, Babel will automatically import the necessary functions from react/jsx-runtime whenever JSX is used, so you don’t have to manually import React.

For TypeScript Users

[[See Video to Reveal this Text or Code Snippet]]

This configuration directs TypeScript to use the new JSX factory, eliminating the need to import React in every file.

Summary

The "React must be in scope when using JSX" error occurs due to the transformation process of JSX to JavaScript relying on the React object being in scope. You can resolve this by:

Importing React in every file using JSX.

Leveraging React 17’s automatic JSX Transform by updating your React and Babel configurations.

Updating TypeScript configuration to use the new JSX factory.

By following these guidelines, you can avoid the "React must be in scope when using JSX" error and streamline your React development process.