React JS is easy and fun to learn. You need to be familiar with HTML, CSS, JavaScript, ES6 features ––Let, Const, Arrow functions, Import and Exports, Classes–– and how to use npm (Node Package Manager).
You can check the official React JS documentation by React. If you have any queries then you can ask for help from the online community. Also, there are other online resources and blogs to learn React JS. After learning React JS, start practicing by implementing small applications such as a to-do app, calculator, etc. For certification, you can enroll in an online course for React JS that provides a good hands-on experience in React JS.
If you are looking for an online course to learn React Js, check out this React Course by Intellipaat.
Also, watch this video to understand: