Google developed the open-source Angular frontend framework, which is based on TypeScript. It assists developers in creating scalable, contemporary online applications, particularly Single Page Applications (SPAs), in which content updates dynamically rather than requiring a page reload. By employing components and services to arrange our code, it facilitates efficient and maintainable development. We must first establish a clear understanding of Angular's definition, structure, and component placement before lifecycle hooks make any sense.

AngularJS vs Angular (Modern Angular)

Feature AngularJS Angular (2+)
Language JavaScript TypeScript
Architecture MVC Component-based
Mobile Support Poor Excellent
Performance Slower Faster (AOT, Tree Shaking)
Development Support Discontinued Actively maintained
Ecosystem Classic JS ecosystem RxJS, TypeScript, CLI

Here’s how the high-level angular structure looks.

Angular Element Purpose School App Example
Modules Organize the app into functional areas StudentModule, TeacherModule, AdminModule, and TimetableModule group features into manageable sections.
Components Handle UI and logic for individual features StudentListComponent, AttendanceFormComponent, and ExamResultsComponent power the core screens of the app.
Templates Define the view using Angular-enhanced HTML A dynamic report card template uses *ngFor to loop through subjects and display student scores.
Services Share business logic and data access across components StudentService centralizes logic to fetch, add, or update student records from the backend.
Routing Enable navigation between pages Angular Router handles navigation to /students, /teachers, /results, and /library.
Directives Add dynamic behavior to templates *ngIf="isAbsent" highlights students in red if they’re absent during the attendance check.
Pipes Format output in templates {{ dateOfBirth | date:'longDate' }} formats a birthday date

What is a Component in Angular?

The core of the user interface in Angular is a component. Usually, every screen, button, form, or card is implemented as a component, much like the Common Language Runtime (CLR) components in.NET. A component is the fundamental unit of the user interface (UI) in Angular. It holds the HTML template, CSS styling, and TypeScript logic for a view, which is a section of the screen that it controls.

Structure of a Component
1. Class contains the logic and data for the component using TypeScript. And File Extension: .ts
@Component({
  selector: 'app-product',         // We can use <app-product></app-product> in HTML
  templateUrl: './product.html',   // Uses product.html for UI
  styleUrls: ['./product.css']     // Uses product.css for styles
})
export class ProductComponent {    // This class holds logic like product name, price, etc.
  name = 'T-Shirt';
  price = 499;
}

2. Template defines the user interface (UI layout) using HTML. It displays data from the class using Angular's data binding.File Extension: .html
<!-- product.component.html -->
<h2>{{ productName }}</h2>
<p>Price: ₹{{ price }}</p>

3. Style adds styling (colors, fonts, spacing) specific to this component. File Extension: .css or .scss

/* product.component.css */
h2 {
  color: blue;
  font-weight: bold;
}

p {
  font-size: 16px;
}

Why are components important for Lifecycle Hooks?
Lifecycle hooks are embedded within components. So, unless you understand how components are created, rendered, and destroyed, lifecycle hooks won’t mean much. Here’s the flow.

  • Angular initializes a component.
  • Angular runs specific hooks at each stage of that component's life.
  • We use those hooks to run our own logic at the perfect moment (like fetching data, unsubscribing, or calculating total).

Angular Lifecycle Hooks
Lifecycle hooks in Angular are special methods that get called automatically at specific stages of a component’s life, from creation to destruction. Lifecycle hooks let Angular manage the creation, change detection, and destruction of components. This gives us fine control over how and when code runs.

Lifecycle hooks are built-in functions that Angular calls at different moments during a component’s lifetime, like when it's created, updated, or destroyed.
Why Use Lifecycle Hooks?

We use lifecycle hooks to,

  • Run initial setup code (like fetching data when the component loads)
  • Detect changes in inputs
  • Perform cleanup tasks (like clearing timers or unsubscribing from services)
  • Debug the flow of your component.


Hook Name When Called Purpose Usage Example
constructor() When a component instance is created Basic initialization of class members (no Angular bindings yet) console.log('Constructor')
ngOnChanges(changes: SimpleChanges) When @Input() property changes Respond to input property changes this.loadData(changes['userId'].currentValue);
ngOnInit() Once after the first ngOnChanges() Fetch data, initialize bindings this.getDataFromService();
ngDoCheck() Every change detection run Custom change tracking logic detectManualChange();
ngAfterContentInit() After content projected via <ng-content> is initialized Set up logic dependent on projected content console.log('ng-content loaded')
ngAfterContentChecked() After every check of the content projection Respond to changes in projected content validateProjectedTemplate();
ngAfterViewInit() After the component’s view (and child views) are initialized DOM access, @ViewChild operations this.chart.init(this.chartElement.nativeElement);
ngAfterViewChecked() After every check of the component and child views Update logic if template data changes adjustLayout();
ngOnDestroy() Just before Angular destroys the component Cleanup (unsubscribe, clear interval) subscription.unsubscribe();

Conclusion
Understanding Angular’s architecture is essential for building modern, scalable, and maintainable web applications. This article walked through the foundational blocks of Angular, Components, Component Lifecycle Hooks, which provide precise control over how Angular creates, updates, and destroys components.