Best UI scalability and rendering

React is the best frontend JavaScript library for efficient rendering of UI components and you can create small components which can then be used to scale the app.

Only JavaScript

Throughout the whole stack JavaScript is the only language used which makes it easier to train people and creates a workspace where resources can be used interchangeably

Easy to test

It is crucial and the first string for the software development process. There are lots of work already done for testing React.js applications, you can use many common tools such as Jest, Mocha, etc.

Open Source

All technologies that are involved in MERN are open-source. This feature allows a developer to get solutions to queries that may evolve during development, from the available open portals. As a result, it will be beneficial for a developer.