CommonJSstyle

CommonJSstyle is a term used to describe JavaScript code that adheres to the CommonJS module pattern as implemented in environments such as Node.js. In this style, each file is a module with its own scope. Dependencies are loaded with the require function and exported values are made available to other modules by assigning to module.exports (or to the exports shorthand). When a module is required, the runtime loads and executes it once and caches its exports for subsequent requests, enabling predictable sharing of modules.

CommonJS modules are loaded synchronously, which fits server-side execution but differs from browser module loading. This approach contributed to the popularity of tools like Browserify and Webpack that allow CommonJS-style modules to run in browsers. In contrast to ES modules, CommonJS uses require and module.exports instead of import and export, and supports dynamic requires, which can limit static analysis.

Best practices within the CommonJSstyle include exporting a single object or function via module.exports, avoiding mixing module.exports with exports, requiring dependencies at the top of the module, and being mindful of circular dependencies which can lead to partially initialized modules.

CommonJSstyle remains common in Node.js ecosystems and npm packages, though many projects are migrating toward ES modules for browser-native code. Interoperability between CommonJS and ES modules is supported in modern runtimes, with some caveats around default imports and live bindings.