What is the difference between using .js vs .jsx files in React?

In a React project, you’ll often see files with the extension .js or .jsx. Technically, both can work for your React components because JSX is compiled into standard JavaScript. However, there are some conventions and tooling features to keep in mind.

1. JSX vs. JavaScript

• JSX: A syntax extension that allows you to write HTML-like elements in JavaScript. For instance, <div>Hello</div> instead of calling React.createElement('div', null, 'Hello').
• JavaScript: The standard .js language file without specific JSX syntax (though you can write normal JavaScript in a .jsx file, too).

2. File Extensions and Tooling

• .jsx: Typically used to indicate that a file contains JSX code. Some linters and IDEs provide extra features (syntax highlighting, lint rules, autocomplete) when they see .jsx.
• .js: A broader extension that may or may not include React/JSX code.

Most bundlers (like Webpack, Vite, etc.) will transpile JSX code whether it’s in a .js or .jsx file, as long as you have the right Babel configuration. Therefore, purely from a build or runtime perspective, there’s no major difference.

3. Conventions

• Team Preference: Some teams prefer .jsx to clearly signal files containing React components, while others keep everything as .js to reduce complexity.
• TypeScript Projects: In a TypeScript React project, you’ll see .tsx for React components (since it indicates both TypeScript + JSX).

4. Best Practices

1. Clarity: Use .jsx if you want to clearly distinguish React component files that contain JSX.
2. Consistency: Stick to one convention across your codebase. This improves readability and reduces confusion for contributors.
3. Tooling Support: Check if your linter or code editor has specific behaviors for .jsx files, such as auto-formatting or lint checks.

Conclusion

Whether you choose .js or .jsx is largely a matter of style and team conventions, since both work under the hood with the same Babel/webpack configurations. The .jsx extension simply clarifies that the file uses JSX, potentially enabling better tooling support and readability for developers.