Node.js DI

Introduction to Dependency Injection

When writing large-scale applications, managing dependencies between modules, classes, and functions can quickly become a headache. This is where dependency injection (DI) comes in.

Dependency injection is a design pattern that helps manage dependencies by providing objects with the dependencies they require, rather than having the objects create the dependencies themselves. This makes code more modular, testable, and maintainable.

What is Node.js DI?

Node.js DI is a library that enables dependency injection in Node.js applications, using either constructor injection or property injection.

Constructor injection involves injecting dependencies into the constructor of a class, while property injection involves injecting dependencies as public properties of a class.

How to use Node.js DI

To use Node.js DI, you must install it as a package via npm:

npm install node-di

Once installed, you can create a DI container, which will hold your dependencies:

const { createContainer } = require('node-di');
const container = createContainer();

You can then register your dependencies with the container:

const MyDependency = require('./my-dependency');

container.register('myDependency', MyDependency);

And finally, you can retrieve your dependencies from the container:

class MyClass {
  constructor(myDependency) {
    this.dependency = myDependency;
  }
}

const myClassInstance = container.resolve(MyClass);

Node.js DI also provides decorators for property injection, making it easier to inject dependencies into class properties:

const { inject } = require('node-di/decorators');

class MyClass {
  @inject('myDependency')
  dependency; // this will be automatically injected with 'myDependency'
}

Conclusion

Node.js DI is a powerful tool for managing dependencies between modules, classes, and functions in Node.js applications. By using DI, you can make your code more modular, testable, and maintainable.