MJS files are JavaScript source code files used as ECMAScript modules. They are designed to be used in modern JavaScript environments, particularly in Node.js and web browsers that support ES modules. Unlike traditional JavaScript files (with the .js extension), MJS files are always parsed as modules, which enforces stricter parsing rules and enables features like import and export statements for managing dependencies and code organization. This modular approach promotes code reusability, maintainability, and better encapsulation. MJS files are typically used for creating reusable components, libraries, and complex applications where modularity is essential. They are often used in conjunction with build tools like Webpack, Parcel, or Rollup to bundle and optimize the code for deployment. The use of MJS files helps to avoid naming conflicts and global scope pollution, leading to more robust and predictable JavaScript applications.