Finding and loading CommonJS and JSON modules using require

We have talked about several types of modules: CommonJS, JSON, ES2015, and native code modules. All but the ES2015 modules are loaded using the require function. That function has a very powerful and flexible algorithm for locating modules within a directory hierarchy. This algorithm, coupled with the npm package management system, gives the Node.js platform a lot of power and flexibility.

File modules

The CommonJS and ES2015 modules we've just looked at are what the Node.js documentation describes as a file module. Such modules are contained within a single file, whose filename ends with .js, .mjs, .json, or .node. The latter are compiled from C or C++ source code, or even other languages such as Rust, while the former are of course written in JavaScript or JSON.

We've already looked at several examples of using these modules, as well as the difference between the CommonJS format traditionally used in Node.js, and the new ES2015 modules...