One of the most powerful things about software development is the ability to reuse and build upon the foundations of other people. This code sharing has helped software progress at an amazing rate. Such a wonderful mechanism is critical on a micro-level for both individual projects and teams. For Node.js, this process of code sharing – both within individual projects and in external npm dependencies – is facilitated using module.exports or exports . How Node Modules Work How do we use module exports to plug an external module, or sensibly break our project down into multiple files (modules)? The Node.js module system was created because its designers didn't want it to suffer from the same problem of broken global scope, like its browser counterpart. They implemented CommonJS specification to achieve this. The two important pieces of the puzzle are module.exports and the require function. How module.exports works module.exports is actually a property of the module object