Big Bang

App.js

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+const Injectable = require('./Injectable')
+
+class App extends Injectable {
+  static services = ['emailLogging']
+  run() {
+    setInterval(() => {
+      this.emailLogging.error('Haha made ya\' look!')
+    }, 5000)
+  }
+}
+
+module.exports = exports = App

DependencyInjector.js

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+const ServiceContainer = require('./ServiceContainer.js')
+
+class DependencyInjector {
+  constructor() {
+    this.container = new ServiceContainer()
+  }
+
+  // Injects the dependencies into an uninstantiated class
+  make(Class) {
+    return Class.__inject(this.container)
+  }
+}
+
+module.exports = exports = DependencyInjector

Injectable.js

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+class Injectable {
+  static services = []
+
+  static __inject(container) {
+    this.services.forEach(serviceName => {
+      this.prototype[serviceName] = container.getService(serviceName)
+    }
+  }
+}
+
+module.exports = exports = Injectable

README.md

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+# Basic Dependency Injection
+## In less than 100 lines of pure, ES6 JavaScript
+
+This is a very bare-bones dependency injector implementation based on the ES6 classes. It's meant to illustrate the feasibility and benefits of using a service-based dependency injector for Node.js/JavaScript applications.
+
+I discuss this project in greater depth in my blog post [here](https://garrettmills.dev/blog).

Service.js

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+class Service {
+
+}
+
+module.exports = exports = Service

ServiceContainer.js

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+const LogHelper = require('./LogHelper')
+const EmailLogHelper = require('./EmailLogHelper')
+
+class ServiceContainer {
+  constructor() {
+    // We define the service classes here, but we won't
+    // instantiate them until they're needed.
+    this.definitions = {
+      logging: LogHelper,
+      emailLogging: EmailLogHelper,
+    }
+
+    // This is where the container will store service instances
+    // so they can be reused when requested.
+    this.instances = {}
+  }
+
+  getService(serviceName) {
+    // Create a service instance if one doesn't already exist.
+    if ( !this.instances[serviceName] ) {
+      const ServiceClass = this.definitions[serviceName]
+      this.instances[serviceName] = new ServiceClass()
+    }
+    return this.instances[serviceName]
+  }
+}
+
+module.exports = exports = ServiceContainer

index.js

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+// Create the dependency injector instance for the application
+const DI = require('./DependencyInjector')
+const di = new DI()
+
+// Now, create the instance of our application using the DI to inject services
+const App = di.make(require('./App'))
+const app = new App() // Has access to the emailLogging service
+
+app.run();