What is the job description of MEAN MERN developer?

What You'll do. Design and build applications/systems based on wireframes and product requirements documents. Work on back-end & front-end development of core scripts using NodeJS/ MongoDB/React. js/Angular/Express /Redux. Unit test code for robustness, including edge cases, usability and general reliability

Should have good knowledge and hands-on experience with Node, js, Express. js, or restify along with other technologies. MERN Stack Developers should know how to build and maintain front-end applications with the help of HTML5, LESS/ SASS, Angular, and other frameworks.

JavaScript (and JSON), the backend, frontend, and database can be operated easily.