Javascript - CommonJs

About

CommonJs ^{1) 2)} is a Module format definition

They have defined:

• a Module
• and packages definition

The CommonJS module proposal specifies a simple API for declaring modules server-side (and unlike AMD) attempts to cover the server side with io, filesystem, promises and more. Due to its history and implementation ³⁾ , using CommonJS modules in the most common of JS environments, the browser, is non-optimal today.

The commonJS format is the default format used by Node.js. Therefore a CommonJS module will run on node.

Syntax

The CommonJS (CJS) list participants ⁴⁾ have worked out the module format.

The CJS mechanisms contain two primary parts:

• export: a variable named exports that contains the public API
• import: a require function that load the module and return the exports variable.

A CJS module does not use any function wrappers such as the AMD define to specify an id or dependencies.

• The module id is the path or module name via a search path
• The dependencies are declared via the require function.

require

Import is done via the require function

// require will import code from another module
var MyDependency = require('my-dependency');

Export

The module exposes its public api via the exports property

// module.exports will make its property public 
exports = ...;

Loader

Server

• Node

Browser

There is not so much adoption of CJS in the browser because:

• many CommonJS APIs address server-oriented features that could not be implement in a browser (for example, io, system and js)
• amd defines already a require function (bringing conflict and confusion)

There was loader but most of them are now no more supported

• curl.js (discontinued 8 years ago - 2014)