Why standalone components matter in Angular - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a standalone component in Angular.

Angular

import { Component } from '@angular/core';

@Component({
  selector: 'app-hello',
  template: `<h1>Hello World</h1>`,
  standalone: [1]
})
export class HelloComponent {}

Drag options to blanks, or click blank then click option'

Afalse

B'yes'

Ctrue

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a boolean for 'standalone'.

Setting 'standalone' to false or null.

Setting standalone: true makes the component standalone, so it doesn't need to be declared in an NgModule.

2fill in blank

medium

Complete the code to import the CommonModule in a standalone component.

Angular

import { Component } from '@angular/core';
import { [1] } from '@angular/common';

@Component({
  selector: 'app-example',
  standalone: true,
  imports: [CommonModule],
  template: `<p>Example works!</p>`
})
export class ExampleComponent {}

Drag options to blanks, or click blank then click option'

AFormsModule

BCommonModule

CRouterModule

DHttpClientModule

Attempts:

3 left

💡 Hint

Common Mistakes

Importing unrelated modules like FormsModule or RouterModule.

Forgetting to import CommonModule when using structural directives.

The CommonModule provides common directives like ngIf and ngFor which are often needed in templates.

3fill in blank

hard

Fix the error in the standalone component declaration by completing the missing property.

Angular

import { Component } from '@angular/core';

@Component({
  selector: 'app-fix',
  template: `<p>Fix me!</p>`,
  [1]: true
})
export class FixComponent {}

Drag options to blanks, or click blank then click option'

Astandalone

Bimports

Cproviders

Dbootstrap

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'imports' or 'providers' instead of 'standalone'.

Omitting the 'standalone' property.

The property standalone must be set to true to declare a standalone component.

4fill in blank

hard

Fill both blanks to create a standalone component that imports FormsModule and declares a template with two-way binding.

Angular

import { Component } from '@angular/core';
import { [1] } from '@angular/forms';

@Component({
  selector: 'app-input',
  standalone: true,
  imports: [[2]],
  template: `<input [(ngModel)]="name" /> <p>Hello {{name}}</p>`
})
export class InputComponent {
  name = '';
}

Drag options to blanks, or click blank then click option'

AFormsModule

BCommonModule

CRouterModule

DHttpClientModule

Attempts:

3 left

💡 Hint

Common Mistakes

Importing CommonModule instead of FormsModule.

Forgetting to add FormsModule to the imports array.

To use two-way binding with ngModel, you must import FormsModule and include it in the imports array.

5fill in blank

hard

Fill all three blanks to create a standalone component that imports RouterModule, uses inject() to get Router, and navigates on button click.

Angular

import { Component, [1] } from '@angular/core';
import { [2], Router } from '@angular/router';

@Component({
  selector: 'app-navigate',
  standalone: true,
  imports: [RouterModule],
  template: `<button (click)="goHome()">Go Home</button>`
})
export class NavigateComponent {
  router = [3](Router);

  goHome() {
    this.router.navigate(['/home']);
  }
}

Drag options to blanks, or click blank then click option'

Ainject

BRouterModule

DRouter

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing 'inject' with 'Injectable'.

Not importing RouterModule or Router correctly.

Using constructor injection instead of inject() function.

Use inject from '@angular/core' to get the Router instance. Import RouterModule for routing features.

Practice

1. What is the main benefit of using standalone: true in an Angular component?

easy

A. It allows the component to work without needing an NgModule.

B. It makes the component run faster in the browser.

C. It automatically adds routing to the component.

D. It converts the component into a service.

Solution

1. Step 1: Understand the role of NgModules

   NgModules group components, but standalone components remove this need.

2. Step 2: Identify what standalone: true does

   This flag makes the component independent, so it doesn't require an NgModule.

3. Final Answer:

   It allows the component to work without needing an NgModule. -> Option A

4. Quick Check:

   Standalone components = no NgModule needed [OK]

Hint: Standalone means no NgModule needed for the component [OK]

Common Mistakes:

• Thinking standalone makes components faster
• Confusing standalone with routing features
• Believing standalone converts components to services

2. Which of the following is the correct way to declare a standalone component in Angular?

easy

A. @NgModule({ standalone: true }) export class ExampleComponent {}

B. @Component({ selector: 'app-example', module: true }) export class ExampleComponent {}

C. @Component({ selector: 'app-example', standalone: true }) export class ExampleComponent {}

D. @Component({ selector: 'app-example' }) export class ExampleComponent {}

Solution

1. Step 1: Recall the syntax for standalone components

   Standalone components use standalone: true inside the @Component decorator.

2. Step 2: Check each option's syntax

   @Component({ selector: 'app-example', standalone: true }) export class ExampleComponent {} correctly uses @Component with standalone: true. Others misuse decorators or omit the flag.

3. Final Answer:

   @Component({ selector: 'app-example', standalone: true }) export class ExampleComponent {} -> Option C

4. Quick Check:

   Standalone flag inside @Component = correct syntax [OK]

Hint: Look for standalone: true inside @Component decorator [OK]

Common Mistakes:

• Using @NgModule instead of @Component
• Writing 'module: true' instead of 'standalone: true'
• Omitting the standalone flag

3. Given this code, what will be the output when AppComponent is rendered?

@Component({ selector: 'app-root', standalone: true, template: `
Hello
`, imports: [ChildComponent] }) export class AppComponent {}
@Component({ selector: 'app-child', standalone: true, template: `
Child works!
` }) export class ChildComponent {}

medium

A. HelloChild works!

B. Hello

C. Error: ChildComponent not declared in NgModule

D. Child works!

Solution

1. Step 1: Check how ChildComponent is included

   AppComponent imports ChildComponent in its imports array, allowing usage in its template.

2. Step 2: Understand standalone component rendering

   Both components are standalone, so ChildComponent renders inside AppComponent's template.

3. Final Answer:

   <h1>Hello</h1><p>Child works!</p> -> Option A

4. Quick Check:

   Standalone imports enable nested component rendering [OK]

Hint: Standalone components must be imported to use in templates [OK]

Common Mistakes:

• Assuming child renders without importing
• Expecting NgModule declaration errors
• Ignoring standalone imports array

4. What is wrong with this standalone component code?

@Component({ selector: 'app-error', standalone: true, template: `
Error component
` }) export class ErrorComponent {}
@Component({ selector: 'app-root', standalone: true, template: ``, imports: [ErrorComponent] }) export class AppComponent {}

medium

A. Standalone components cannot have templates.

B. AppComponent does not import ErrorComponent in its imports array.

C. The selector 'app-error' is invalid for standalone components.

D. ErrorComponent should not be standalone if used inside another component.

Solution

1. Step 1: Check component imports for nested usage

   AppComponent uses <app-error> but does not import ErrorComponent in its imports array.

2. Step 2: Understand standalone component import rules

   Standalone components must import other standalone components they use in templates.

3. Final Answer:

   AppComponent does not import ErrorComponent in its imports array. -> Option B

4. Quick Check:

   Missing import of nested standalone component causes error [OK]

Hint: Always import standalone components you use inside templates [OK]

Common Mistakes:

• Thinking standalone components don't need imports
• Believing selectors are restricted for standalone
• Assuming standalone components can't have templates

5. You want to create a reusable button component as standalone and use it in multiple other standalone components without NgModules. Which approach is correct?

hard

A. Create the button without standalone and declare it in a shared NgModule imported everywhere.

B. Create the button as a directive and add it to the root NgModule.

C. Create the button as a service and inject it into components.

D. Create the button with standalone: true and import it in each component's imports array where used.

Solution

1. Step 1: Understand standalone component reuse

   Standalone components can be reused by importing them directly in other standalone components.

2. Step 2: Identify the correct reuse method without NgModules

   Create the button with standalone: true and import it in each component's imports array where used. uses standalone: true and imports the button in each component, avoiding NgModules.

3. Final Answer:

   Create the button with standalone: true and import it in each component's imports array where used. -> Option D

4. Quick Check:

   Standalone reuse = import in each component [OK]

Hint: Import standalone components where needed; no NgModules required [OK]

Common Mistakes:

• Trying to use NgModules with standalone components
• Confusing services with UI components
• Using directives instead of components for buttons