Component template basics in Angular - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What will this Angular component template display?

Given the component template below, what text will be shown in the browser?

Angular

<div>
  <h1>{{ title }}</h1>
  <p *ngIf="showDescription">Welcome to Angular!</p>
</div>

A Displays a heading 'Hello Angular' and the paragraph 'Welcome to Angular!'

B Displays only the heading 'Hello Angular' with no paragraph

C Displays nothing because of a syntax error

D Displays the paragraph 'Welcome to Angular!' but no heading

💡 Hint

Look at the *ngIf directive and the interpolation syntax.

The {{ title }} shows the string 'Hello Angular'. The *ngIf directive shows the paragraph only if showDescription is true. Since it is true, both heading and paragraph appear.

📝 Syntax

intermediate

Which template syntax is correct for binding a button click event?

Choose the correct Angular template syntax to call onClick() when a button is clicked.

A <button [click]="onClick()">Click me</button>

B <button (click)="onClick()">Click me</button>

C <button {click}="onClick()">Click me</button>

D <button #click="onClick()">Click me</button>

💡 Hint

Angular uses parentheses for event binding.

The correct syntax for event binding uses parentheses around the event name, like (click). Square brackets are for property binding.

❓ state_output

advanced

What is the output of this Angular template with a loop?

Given the component code below, what will the template render?

Angular

<ul>
  <li *ngFor="let item of items; index as i">{{ i }}: {{ item }}</li>
</ul>

A <ul><li>Apple</li><li>Banana</li><li>Cherry</li></ul>

B <ul><li>1: Apple</li><li>2: Banana</li><li>3: Cherry</li></ul>

C <ul><li>0: Apple</li><li>1: Banana</li><li>2: Cherry</li></ul>

D Syntax error due to incorrect *ngFor syntax

💡 Hint

Remember that index as i starts counting from zero.

The *ngFor directive loops over items. The index as i gives the zero-based index. So the list shows indices 0, 1, 2 with their items.

🔧 Debug

advanced

Why does this Angular template cause an error?

Examine the template code below. Why does Angular throw an error when rendering?

Angular

<div>
  <p>{{ user.name }}</p>
</div>

A Because <code>user.name</code> is a function and cannot be used in interpolation

B Because interpolation syntax must use square brackets instead of curly braces

C Because Angular templates cannot access nested object properties

D Because <code>user</code> is undefined or null, so <code>user.name</code> causes an error

💡 Hint

Think about what happens if user is not set yet.

If user is null or undefined, trying to access user.name causes a runtime error. Use safe navigation operator user?.name to avoid this.

🧠 Conceptual

expert

How does Angular's template binding update the view when component state changes?

Which statement best describes how Angular updates the view when a component's property changes?

A Angular uses a change detection mechanism that compares old and new values and updates the DOM only where changes occur

B Angular re-renders the entire component template from scratch every time any property changes

C Angular requires manual DOM updates using native JavaScript when component properties change

D Angular updates the view only when the user triggers a manual refresh event

💡 Hint

Think about how Angular efficiently keeps the view in sync with data.

Angular's change detection checks component properties and updates only the parts of the DOM that need to change, making updates efficient.