Microsoft007

low-level Angular architecture diagram showing what happens internally when you create and run an app (ng new sampleapp + ng serve), and how execution flows through files like main.ts, app.module.ts, app.component.ts, app.html, etc., especially where debugging breakpoints (step over, step into) are effective.

Here’s a detailed breakdown and flow + diagram explanation 👇

🧩 1. Angular Application Structure (after `ng new sampleapp`)


sampleapp/
 ├── src/
 │   ├── main.ts
 │   ├── index.html
 │   ├── styles.css
 │   ├── app/
 │   │    ├── app.module.ts
 │   │    ├── app.component.ts
 │   │    ├── app.component.html
 │   │    ├── app.component.css
 │   │    ├── app.routes.ts (or app-routing.module.ts)
 │   │    ├── app.component.spec.ts
 ├── angular.json
 ├── package.json
 ├── tsconfig.json

⚙️ 2. Runtime Flow (Execution Order)

(A) `ng serve`

Compiles and serves your Angular app in development mode.
Uses Webpack Dev Server to bundle TS → JS → browser.

(B) `main.ts`

Entry Point


platformBrowserDynamic()
  .bootstrapModule(AppModule)
  .catch(err => console.error(err));

👉 Starts the Angular app by bootstrapping AppModule.

🟩 Breakpoints:
Set breakpoints here to debug initial app bootstrap (first executed file).

(C) `app.module.ts`

Root Module Definition


@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule, AppRoutingModule],
  bootstrap: [AppComponent]
})
export class AppModule {}

👉 Registers components and modules.

🟩 Breakpoints:
Place in constructor or ngOnInit() (if any service injected).

(D) `app.component.ts`

Root Component


@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  title = 'sampleapp';
  constructor() { }
  ngOnInit() { console.log('AppComponent loaded'); }
}

🟩 Breakpoints:

constructor()
ngOnInit()
This is where runtime logic starts when UI is rendered.

(E) `app.component.html`

Template for AppComponent


<h1>{{ title }}</h1>
<router-outlet></router-outlet>

👉 UI rendering happens here.

🟩 Breakpoints:
No TS breakpoints — but inspect DOM via browser DevTools.

(F) `app.routes.ts` (or `app-routing.module.ts`)

Routing setup


const routes: Routes = [
  { path: '', component: HomeComponent },
  { path: 'about', component: AboutComponent }
];

👉 Controls navigation paths.

🟩 Breakpoints:
In constructor of routed components or ngOnInit().

(G) `app.spec.ts`

Unit Testing File


describe('AppComponent', () => {
  it('should create the app', () => { ... });
});

👉 Runs only during testing (ng test), not ng serve.

(H) `index.html`

Root HTML


<body>
  <app-root></app-root>
</body>

👉 Angular replaces <app-root> with AppComponent content.

(I) `styles.css`

Global Styles

Affects all components (like body font, layout, etc.).

🧠 3. Debugging Step-by-Step (VS Code)

🧩 To enable debugging:

Open project in VS Code
Go to Run → Add Configuration → Chrome Launch
It creates .vscode/launch.json
Run app: ng serve
Press F5 to launch debugger

🟩 Set breakpoints in:

main.ts → Entry point
app.module.ts → Module load
app.component.ts → Component init
Any other service or lifecycle hook

Use Step Over (F10), Step Into (F11), Continue (F5).

📊 4. Low-Level Angular Flow Diagram (Text Version)


Browser loads index.html
        │
        ▼
   main.ts (bootstrap Angular)
        │
        ▼
  AppModule initialized
        │
        ▼
  AppComponent created
        │
        ▼
  app.component.html rendered
        │
        ▼
  Routing activated (if any)
        │
        ▼
  Other components load (as per routes)
        │
        ▼
  UI displayed and ready for interaction

If you’d like, I can generate a professional diagram (with arrows, modules, and lifecycle flow) showing exactly:

Entry points (main.ts → AppModule → AppComponent)
Routing
HTML/CSS connection
Debugging breakpoint icons (🟥 for active breakpoints)

Monday, 6 October 2025

Angular Application Structure

🧩 1. Angular Application Structure (after ng new sampleapp)

⚙️ 2. Runtime Flow (Execution Order)

(A) ng serve

(B) main.ts

(C) app.module.ts

(D) app.component.ts

(E) app.component.html

(F) app.routes.ts (or app-routing.module.ts)

(G) app.spec.ts

(H) index.html

(I) styles.css