Component template basics in Angular - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to display a title in the component template.

Angular

<h1>[1]</h1>

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

Atitle

BTitle

Cthis.title

Dcomponent.title

Attempts:

3 left

💡 Hint

Common Mistakes

Using this.title inside the template binding.

Using a string literal instead of the property name.

The template uses {{title}} to bind the component's title property.

2fill in blank

medium

Complete the code to bind the button click event to the onClick method.

Angular

<button ([1])="onClick()">Click me</button>

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

Atap

Bclick

CclickEvent

DonClick

Attempts:

3 left

💡 Hint

Common Mistakes

Using the method name instead of the event name inside parentheses.

Using incorrect event names like tap.

The Angular event binding syntax uses parentheses with the event name, like (click).

3fill in blank

hard

Fix the error in the template to correctly display the user's name property.

Angular

<p>Hello, [1]</p>

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

Athis.user.name

BuserName

Cuser.name

Duser->name

Attempts:

3 left

💡 Hint

Common Mistakes

Using this.user.name inside the template.

Using invalid syntax like user->name.

Use dot notation to access nested properties in the template without this.

4fill in blank

hard

Fill both blanks to bind the input value and update the username property.

Angular

<input [[1]]="username" ([2])="username = $event.target.value">

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

Avalue

Binput

Cclick

Dchecked

Attempts:

3 left

💡 Hint

Common Mistakes

Using click event instead of input.

Binding to checked instead of value.

The input's value property is bound with square brackets, and the input event updates the property.

5fill in blank

hard

Fill all three blanks to create a list displaying each item from the items array.

Angular

<ul>
  <li *ngFor="let [1] of [2]; [3]" >[1]</li>
</ul>

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

Aitem

Bitems

CtrackBy: trackById

DtrackBy

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect variable names like items instead of item.

Using plain trackBy instead of trackBy: trackById syntax.

The *ngFor directive loops over items with item as the variable. The trackBy: trackById input helps Angular track items efficiently.

Practice

1. What is the main purpose of a component template in Angular?

easy

A. To style the component with CSS

B. To write backend server logic

C. To configure routing paths

D. To define the HTML structure and dynamic content users see

Solution

1. Step 1: Understand what a component template does

   A component template controls what the user sees by defining HTML and dynamic content.

2. Step 2: Compare options to this role

   Only To define the HTML structure and dynamic content users see describes this role correctly; others relate to different parts of Angular.

3. Final Answer:

   To define the HTML structure and dynamic content users see -> Option D

4. Quick Check:

   Component template = HTML + dynamic content [OK]

Hint: Templates show what users see and interact with [OK]

Common Mistakes:

• Confusing templates with backend logic
• Thinking templates handle styling only
• Mixing templates with routing configuration

2. Which of the following is the correct syntax to bind a component property title to an h1 tag in the template?

easy

A. {{ title }}

B. [title]

C. (title)

D. { title }

Solution

1. Step 1: Recall Angular interpolation syntax

   Angular uses double curly braces {{ }} to display component properties in templates.

2. Step 2: Match options with correct syntax

   Only

   {{ title }}

   uses {{ title }} correctly; others use invalid or incorrect brackets.

3. Final Answer:

   <h1>{{ title }}</h1> -> Option A

4. Quick Check:

   Interpolation uses {{ }} [OK]

Hint: Use {{ }} to show variables in templates [OK]

Common Mistakes:

• Using square brackets [] for interpolation
• Using parentheses () instead of curly braces
• Forgetting to use double curly braces

3. Given this component template snippet:

<button (click)="increment()">Add</button>
<p>Count: {{ count }}</p>

And the component code:

count = 0;
increment() { this.count++; }

What will be displayed after clicking the button three times?

medium

A. Count: 3

B. Count: 0

C. Count: 1

D. Count: undefined

Solution

1. Step 1: Understand the initial state and method

   The count starts at 0. Each click calls increment(), which adds 1 to count.

2. Step 2: Calculate count after three clicks

   After 3 clicks, count = 0 + 3 = 3, so template shows 'Count: 3'.

3. Final Answer:

   Count: 3 -> Option A

4. Quick Check:

   3 clicks increment count to 3 [OK]

Hint: Click calls method that adds 1 each time [OK]

Common Mistakes:

• Thinking count resets after each click
• Confusing event binding syntax
• Ignoring the initial count value

4. Identify the error in this Angular template snippet:

<div>
  <p>User: {{ userName }}</p>
  <button (click)="updateName('Alice')">Change Name</button>
</div>

Assuming userName and updateName exist in the component, what is wrong?

medium

A. The event binding syntax (click) is incorrect

B. The template is correct; no errors

C. The method call inside (click) should not have quotes around 'Alice'

D. Interpolation {{ userName }} should be inside square brackets

Solution

1. Step 1: Check event binding syntax

   (click) is the correct way to bind click events in Angular templates.

2. Step 2: Verify method call and interpolation

   Calling updateName('Alice') with quotes is valid. Interpolation uses {{ }} correctly.

3. Final Answer:

   The template is correct; no errors -> Option B

4. Quick Check:

   Event binding and interpolation syntax are correct [OK]

Hint: Event binding uses (event)="method()" with quotes [OK]

Common Mistakes:

• Removing quotes from string arguments in method calls
• Using square brackets for interpolation
• Miswriting event binding syntax

5. You want to display a list of items stored in the component property items = ['Apple', 'Banana', 'Cherry']. Which template snippet correctly shows each item in an unordered list?

hard

A.
{{ items }}

B.
{{ item }}

C.
{{ item }}

D.
{{ item }}

Solution

1. Step 1: Recall correct *ngFor syntax

   The correct syntax is *ngFor="let variable of collection" to loop over items.

2. Step 2: Evaluate each option

   Only <ul> <li *ngFor="let item of items">{{ item }}</li> </ul> uses the correct syntax; the others use invalid variations like "items as item", reversed order with "in", or missing "let".

3. Final Answer:

   <ul> <li *ngFor="let item of items">{{ item }}</li> </ul> -> Option C

4. Quick Check:

   *ngFor="let x of y" loops correctly [OK]

Hint: Use *ngFor="let item of items" to loop lists [OK]

Common Mistakes:

• Swapping 'of' with 'as' or 'in'
• Using plural variable names incorrectly
• Forgetting 'let' keyword in *ngFor