Standalone component declaration in Angular - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a standalone component in Angular?

A standalone component is an Angular component that does not require being declared inside an NgModule. It can be used independently and imported directly where needed.

beginner

How do you declare a component as standalone in Angular?

You add the property standalone: true in the @Component decorator metadata.

intermediate

Can standalone components import other standalone components or Angular modules?

Yes, standalone components can import other standalone components, directives, pipes, or Angular modules using the <code>imports</code> array in the <code>@Component</code> decorator.

intermediate

What is the benefit of using standalone components in Angular?

Standalone components simplify Angular apps by reducing the need for NgModules, making the code easier to read, maintain, and enabling faster compilation.

beginner

Show a simple example of a standalone component declaration in Angular.

Example:<br><pre>import { Component } from '@angular/core';

@Component({
  selector: 'app-hello',
  standalone: true,
  template: `<h1>Hello, Angular!</h1>`
})
export class HelloComponent {}</pre>

What property must be set to true to make an Angular component standalone?

A standalone

B independent

C moduleFree

D selfContained

The property standalone: true in the component decorator makes it a standalone component.

Can a standalone component be used without declaring it in an NgModule?

A No, it must be declared in an NgModule.

B Only if it imports an NgModule.

C Yes, it can be used directly.

D Only in Angular versions before 14.

Standalone components do not require NgModule declarations and can be used directly.

Where do you specify other components or modules a standalone component uses?

A In the bootstrap array inside NgModule.

B In the declarations array inside NgModule.

C In the providers array inside the component.

D In the imports array inside the @Component decorator.

Standalone components use the imports array inside the @Component decorator to include other components or modules.

Which Angular version introduced standalone components?

A Angular 12

B Angular 14

C Angular 10

D Angular 16

Standalone components were introduced in Angular 14.

What is a key advantage of standalone components?

A They reduce the need for NgModules.

B They require more boilerplate code.

C They cannot import other components.

D They only work with class components.

Standalone components simplify app structure by reducing the need for NgModules.

Explain how to create a standalone component in Angular and why it might be useful.

Think about how Angular components usually need NgModules and how standalone changes that.

Describe how standalone components handle dependencies like other components or Angular modules.

Consider where you specify what a component needs to work.

Practice

1. What does adding standalone: true in an Angular component's decorator do?

easy

A. Disables change detection for the component.

B. Makes the component lazy-loaded automatically.

C. Registers the component globally in the Angular app.

D. Declares the component as standalone, removing the need for NgModule declaration.

Solution

1. Step 1: Understand Angular component declaration

   Normally, Angular components must be declared inside an NgModule to be usable.

2. Step 2: Effect of standalone: true

   Setting standalone: true allows the component to be used without declaring it in any NgModule.

3. Final Answer:

   Declares the component as standalone, removing the need for NgModule declaration. -> Option D

4. Quick Check:

   Standalone component = no NgModule needed [OK]

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

Common Mistakes:

• Thinking standalone makes component lazy-loaded
• Assuming standalone registers component globally
• Confusing standalone with change detection settings

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

easy

A. @Component({ selector: 'app-test', standalone: true, template: 'Test' }) export class TestComponent {}

B. @Component({ selector: 'app-test', standalone: false, template: 'Test' }) export class TestComponent {}

C. @Component({ selector: 'app-test', standalone: true, templateUrl: 'test.html' }) export class TestComponent {} NgModule({ declarations: [TestComponent] })

D. @Component({ selector: 'app-test', standalone: true }) export class TestComponent { template: 'Test' }

Solution

1. Step 1: Check the standalone property usage

   The standalone property must be set to true inside the @Component decorator.

2. Step 2: Verify template declaration and class export

   The template can be inline with template or external with templateUrl. The class must be exported properly.

3. Final Answer:

   @Component({ selector: 'app-test', standalone: true, template: '<p>Test</p>' }) export class TestComponent {} -> Option A

4. Quick Check:

   Standalone true inside @Component with inline template [OK]

Hint: Standalone true must be inside @Component decorator [OK]

Common Mistakes:

• Setting standalone to false
• Declaring template outside the decorator
• Mixing NgModule declaration with standalone component

3. Given this standalone component declaration, what will be the rendered output?

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

@Component({
  selector: 'app-hello',
  standalone: true,
  template: `
Hello, {{ name }}!
`
})
export class HelloComponent {
  name = 'Angular';
}

medium

A. No output because component is standalone

B. Hello, {{ name }}!

C. Hello, Angular!

D. Error: Property 'name' is undefined

Solution

1. Step 1: Understand template interpolation

   The template uses {{ name }} which Angular replaces with the component's property value.

2. Step 2: Check the property value

   The component defines name = 'Angular', so interpolation outputs 'Angular'.

3. Final Answer:

   <h1>Hello, Angular!</h1> -> Option C

4. Quick Check:

   Template interpolation replaces {{ name }} with 'Angular' [OK]

Hint: Interpolation shows property value inside template [OK]

Common Mistakes:

• Thinking interpolation shows raw {{ name }}
• Assuming standalone disables property binding
• Expecting runtime error for missing property

4. Identify the error in this standalone component declaration:

@Component({
  selector: 'app-sample',
  standalone: true,
  template: '
Sample
',
  imports: [CommonModule]
})
export class SampleComponent {}

medium

A. The imports array must be inside @NgModule, not @Component

B. Missing import statement for CommonModule

C. CommonModule must be imported from '@angular/common' and declared in imports

D. CommonModule cannot be imported in standalone components

Solution

1. Step 1: Check imports usage in standalone component

   Standalone components can import modules like CommonModule via the imports array in the decorator.

2. Step 2: Verify import statement presence

   The code uses CommonModule in imports but does not import it from '@angular/common' at the top.

3. Final Answer:

   Missing import statement for CommonModule -> Option B

4. Quick Check:

   Imports array needs proper import statements [OK]

Hint: Always import modules before using in imports array [OK]

Common Mistakes:

• Thinking imports array is invalid in @Component
• Forgetting to import CommonModule from '@angular/common'
• Assuming CommonModule cannot be used in standalone components

5. You want to create a standalone Angular component that uses another standalone component called ButtonComponent. How should you declare the imports array in your component decorator?

hard

A. @Component({ standalone: true, imports: [ButtonComponent], template: '' })

B. @Component({ standalone: true, imports: ['ButtonComponent'], template: '' })

C. @Component({ standalone: true, imports: [NgModule], template: '' })

D. @Component({ standalone: true, template: '' })

Solution

1. Step 1: Understand how to use other standalone components

   Standalone components can import other standalone components by listing them in the imports array.

2. Step 2: Correct syntax for imports array

   The imports array must contain the component class itself, not a string or NgModule.

3. Final Answer:

   @Component({ standalone: true, imports: [ButtonComponent], template: '<app-button></app-button>' }) -> Option A

4. Quick Check:

   Imports array includes component classes, not strings [OK]

Hint: Import component classes directly, not strings or modules [OK]

Common Mistakes:

• Using string names instead of component classes in imports
• Importing NgModule instead of component
• Omitting imports array when using other standalone components