From da706a9c5a335093ee36a1ef46ad1a81a57a6757 Mon Sep 17 00:00:00 2001
From: garrettmills <garrett@garrettmills.dev>
Date: Fri, 15 Nov 2019 21:30:27 -0600
Subject: [PATCH] Big Bang

---
 App.js                | 12 ++++++++++++
 DependencyInjector.js | 14 ++++++++++++++
 Injectable.js         | 11 +++++++++++
 README.md             |  6 ++++++
 Service.js            |  5 +++++
 ServiceContainer.js   | 28 ++++++++++++++++++++++++++++
 index.js              |  9 +++++++++
 7 files changed, 85 insertions(+)
 create mode 100644 App.js
 create mode 100644 DependencyInjector.js
 create mode 100644 Injectable.js
 create mode 100644 README.md
 create mode 100644 Service.js
 create mode 100644 ServiceContainer.js
 create mode 100644 index.js

diff --git a/App.js b/App.js
new file mode 100644
index 0000000..fa4a87c
--- /dev/null
+++ b/App.js
@@ -0,0 +1,12 @@
+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
diff --git a/DependencyInjector.js b/DependencyInjector.js
new file mode 100644
index 0000000..274f51a
--- /dev/null
+++ b/DependencyInjector.js
@@ -0,0 +1,14 @@
+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
diff --git a/Injectable.js b/Injectable.js
new file mode 100644
index 0000000..222595b
--- /dev/null
+++ b/Injectable.js
@@ -0,0 +1,11 @@
+class Injectable {
+  static services = []
+
+  static __inject(container) {
+    this.services.forEach(serviceName => {
+      this.prototype[serviceName] = container.getService(serviceName)
+    }
+  }
+}
+
+module.exports = exports = Injectable
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..afb7f74
--- /dev/null
+++ b/README.md
@@ -0,0 +1,6 @@
+# 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).
\ No newline at end of file
diff --git a/Service.js b/Service.js
new file mode 100644
index 0000000..4c1b62d
--- /dev/null
+++ b/Service.js
@@ -0,0 +1,5 @@
+class Service {
+
+}
+
+module.exports = exports = Service
diff --git a/ServiceContainer.js b/ServiceContainer.js
new file mode 100644
index 0000000..b3df940
--- /dev/null
+++ b/ServiceContainer.js
@@ -0,0 +1,28 @@
+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
diff --git a/index.js b/index.js
new file mode 100644
index 0000000..b8d746e
--- /dev/null
+++ b/index.js
@@ -0,0 +1,9 @@
+// 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();