ReactJS is a popular JavaScript library used for building user interfaces. It is widely used in web development, and many developers are interested in learning this library. Here are some resources where you can learn ReactJS for free:

1. React documentation: The official React documentation is the best place to start learning ReactJS. It provides a comprehensive guide to ReactJS, including basics, advanced concepts, and tutorials. You can find the documentation at reactjs.org/docs/getting-started.html.

2. FreeCodeCamp: FreeCodeCamp offers a comprehensive ReactJS course that covers everything you need to know to get started with React. The course includes video tutorials, interactive coding challenges, and projects. You can find the course at freecodecamp.org/learn/front-end-libraries/...

3. React for Beginners: This is a free course that covers the basics of ReactJS. It includes video tutorials and coding exercises. You can find the course at reactforbeginners.com.

4. Codecademy: Codecademy offers a free ReactJS course that covers the basics of ReactJS. It includes video tutorials, coding exercises, and projects. You can find the course at codecademy.com/learn/react-101.

5. React Crash Course: This is a free video tutorial that covers the basics of ReactJS. It is a great resource for beginners who want to get started with React. You can find the tutorial at youtube.com/watch?v=Ke90Tje7VS0.

6. Udemy: Udemy offers many ReactJS courses, and some of them are free. You can find courses that cover the basics of ReactJS, as well as advanced topics. You can find the courses at udemy.com/topic/react.

7. Scrimba: Scrimba offers free interactive video tutorials on ReactJS. You can follow along with the tutorials, pause and rewind as needed, and even edit the code in the video. You can find the tutorials at scrimba.com/learn/learnreact.

8. ReactJS Fundamentals: This is a free course that covers the basics of ReactJS. It includes video tutorials and coding exercises. You can find the course at tylermcginnis.com/courses/react-fundamentals.

9. Egghead: Egghead offers many free ReactJS courses, including courses on React Hooks, React Router, and Redux. You can find the courses at egghead.io/browse/libraries/react.

10. React Native: If you are interested in learning React Native, the official documentation is a great place to start. It provides a comprehensive guide to React Native, including basics, advanced concepts, and tutorials. You can find the documentation at reactnative.dev/docs/getting-started.

Learning ReactJS is a great investment in your web development career. With these free resources, you can get started with ReactJS and build amazing user interfaces.