How Do I create a NodeJS Module?

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I have read the details on NodeJS site : https://nodejs.org/api/modules.html. I don't understand how modules work, and what are the minimal steps for creating a module, and how npm can help me.

How can I create a module?
How do I use a module?
What does putting it on npm mean?

Note: this is a self answered question, with the purpose of sharing knowledge as a canonical.

node.js
3 Answers

There are two main ways for wiring modules. One of them is using hard coded dependencies, explicitly loading one module into another using a require call. The other method is to use a dependency injection pattern, where we pass the components as a parameter or we have a global container (known as IoC, or Inversion of Control container), which centralizes the management of the modules.

We can allow Node.js to manage the modules life cycle by using hard coded module loading. It organizes your packages in an intuitive way, which makes understanding and debugging easy.

Dependency Injection is rarely used in a Node.js environment, although it is a useful concept. The DI pattern can result in an improved decoupling of the modules. Instead of explicitly defining dependencies for a module, they are received from the outside. Therefore they can be easily replaced with modules having the same interfaces.

Let’s see an example for DI modules using the factory pattern:

class Car {
  constructor (options) {
    this.engine = options.engine
  }

  start () {
    this.engine.start()
  }
}

function create (options) {
  return new Car(options)
}

module.exports = create
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