The fundamental advantage of the MERN stack in web development is that every line of code is written in JavaScript, which is a nearly global programming language because it is required for both server-side and client-side code. The MERN stack eliminates context switching and substantially simplifies the entire development process by employing a single programming language, offering web developers the tools they need to construct effective online apps with far less work.
Those who utilise technology stacks that use various programming languages must figure out how to correctly interface them on their own, whereas developers who use a JavaScript stack like MERN simply need to know JavaScript and JSON.