What is the Angular CLI, and how do you use it? The Angular CLI (Command Line Interface) is a tool to create, build, test, and deploy

ngular applications.

Common Commands:

ng new my-app # Create new Angular project

ng serve # Run development server

ng generate component login # Generate component

ng build # Build for production

ng test # Run unit tests

Real-Time Example:

In a company, developers use ng generate component invoice to create a new

invoice component with all required files.

ngular Components & Templates

The @Component decorator defines a component in Angular. It tells Angular how to create

nd display the component by providing metadata such as the selector, template, and

styles.

✅ Example:

@Component({

selector: 'app-user-card',

templateUrl: './user-card.component.html',

styleUrls: ['./user-card.component.css']

})

export class UserCardComponent {}

📌 Real-Time Example:

In a CRM app, @Component({ selector: 'app-customer' }) is used to define a

reusable customer display card.

the different types.

Data binding connects the component's class logic with its template (HTML).

✳ Types of Data Binding:

Type Syntax Description

Interpolation 	{{ value }} 	Bind component data to HTML

Property Binding [property]="val

ue"

Bind DOM properties to component

Event Binding (event)="handle

r()"

Bind DOM events to component methods

Two-Way Binding [(ngModel)]="va

lue"

Sync data both ways (input ↔

component)

✅ Example:

<!-- Interpolation -->

<h1>{{ title }}</h1>

<!-- Property Binding -->

<input [value]="name" />

<!-- Event Binding -->

<button (click)="greetUser()">Greet</button>

<!-- Two-Way Binding -->

<input [(ngModel)]="username" />

in templates?

• *ngIf: Conditionally includes or removes an element.
• *ngFor: Iterates over a list and renders template for each item.

✅ Example:

<!-- *ngIf -->

<div *ngIf="isLoggedIn">Welcome, {{ user.name }}</div>

<!-- *ngFor -->

<ul>

<li *ngFor="let product of products">{{ product.name }}</li>

</ul>

📌 Real-Time Example:

E-commerce product list: *ngFor displays product cards dynamically.

ngular?

➤ Parent to Child: Use @Input()

// child.component.ts

@Input() userData: any;

<!-- parent.component.html -->

<app-child [userData]="user"></app-child>

➤ Child to Parent: Use @Output() + EventEmitter

// child.component.ts

@Output() notify = new EventEmitter<string>();

this.notify.emit('Hello Parent!');

<!-- parent.component.html -->

<app-child (notify)="handleNotification($event)"></app-child>

📌 Real-Time Example:

• Pass user object to UserCardComponent via @Input.
• Emit "user clicked" event back to parent with @Output.

describe them.

Lifecycle hooks are methods that Angular calls at specific stages of a component's

existence.

🌀 Common Lifecycle Hooks:

Hook Description

ngOnInit Called once after component is initialized

ngOnChanges Called when input properties change

ngDoCheck Called during every change detection

ngAfterViewI

nit

Called after component’s view has been initialized

ngOnDestroy Cleanup just before the component is destroyed

ngOnChanges() is called whenever an @Input() property changes in the component.

✅ Example:

@Input() user: User;

ngOnChanges(changes: SimpleChanges) {

console.log('User changed:', changes.user.currentValue);

}

📌 Real-Time Example:

When a new user is selected in a dashboard, ngOnChanges() updates the user detail card

dynamically.

do you implement it?

Two-way data binding means synchronizing the view and the component model

utomatically.

✅ Syntax:

<input [(ngModel)]="username" />

Requires importing FormsModule.

📌 Real-Time Example:

In a login form, updating the email input field updates the email property in the component

instantly.

ngular provides two ways:

➤ Template-Driven Forms:

Use ngModel, required, etc.

<form #form="ngForm">

<input name="email" [(ngModel)]="email" required />

<div *ngIf="form.controls.email?.invalid">Email is required.</div>

</form>

➤ Reactive Forms:

Use FormGroup, FormControl, and Validators.

form = new FormGroup({

email: new FormControl('', [Validators.required,

Validators.email])

});

📌 Real-Time Example:

Login or signup forms showing real-time validation messages.

Use Reactive Forms to generate controls at runtime.

✅ Example:

form: FormGroup;

constructor(private fb: FormBuilder) {}

ngOnInit() {

this.form = this.fb.group({});

this.questions.forEach(q => {

this.form.addControl(q.key, new FormControl(''));

});

}

📌 Real-Time Example:

Survey builder where form fields change based on user selections.

be used?

ngModel is a directive that enables two-way data binding in template-driven forms.

✅ Example:

<input [(ngModel)]="name" />

Use it when:

• Working with template-driven forms
• Simple input binding is sufficient

Must import FormsModule.

📌 Real-Time Example:

Live search input field using [(ngModel)]="searchQuery" for filtering products.

ngular Directives

ttribute directives in Angular?

➤ Structural Directives:

• Change the structure/layout of the DOM by adding or removing elements.
• Prefix: * (e.g., *ngIf, *ngFor)

Examples:

• *ngIf – conditionally includes elements
• *ngFor – loops over data to render elements
• *ngSwitch – conditionally renders one view out of many

➤ Attribute Directives:

• Change the appearance or behavior of an existing DOM element or component.

Examples:

• ngClass – dynamically sets CSS classes
• ngStyle – sets inline styles dynamically
• Custom highlight directive (e.g., change color on hover)

✅ Real-Time Analogy:

• Structural: Like building or removing walls in a house (changes structure).
• Attribute: Like painting the walls (changes appearance only).

directives in Angular?

➤ *ngIf: Conditionally displays content

<div *ngIf="isLoggedIn">Welcome!</div>

➤ *ngFor: Iterates over a list

<li *ngFor="let item of items">{{ item.name }}</li>

➤ ngSwitch: Selectively renders based on a condition

<div [ngSwitch]="status">

<p *ngSwitchCase="'active'">Active</p>

<p *ngSwitchCase="'inactive'">Inactive</p>

<p *ngSwitchDefault>Unknown</p>

</div>

ngular?

➤ Steps: