Why pipes are needed in Angular - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to use a pipe that formats a date in Angular.

Angular

<p>{{ today [1] date:'shortDate' }}</p>

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

A|

B:

C.

D#

Attempts:

3 left

💡 Hint

Common Mistakes

Using ':' instead of '|' to apply a pipe.

In Angular, pipes are used with the | symbol to transform data in templates.

2fill in blank

medium

Complete the code to transform a string to uppercase using a pipe.

Angular

<p>{{ name [1] uppercase }}</p>

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

A|

B#

C.

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Using ':' or '.' instead of '|' for pipes.

The | symbol is used to apply pipes like uppercase in Angular templates.

3fill in blank

hard

Fix the error in the code to correctly format a number with a pipe.

Angular

<p>{{ amount [1] currency }}</p>

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

A:

B#

C.

D|

Attempts:

3 left

💡 Hint

Common Mistakes

Using ':' instead of '|' causes syntax errors.

The pipe symbol | is required to apply the currency pipe in Angular.

4fill in blank

hard

Complete the code to create a pipe that formats a number as a percent with two decimals.

Angular

<p>{{ value [1] percent : '1.2-2' }}</p>

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

A|

B:

C,

D.

Attempts:

3 left

💡 Hint

Common Mistakes

Using ',' or '.' instead of ':' for pipe parameters.

The pipe symbol | applies the pipe, and : passes parameters to the pipe.

5fill in blank

hard

Complete the code to chain pipes that first uppercase a string and then slice it.

Angular

<p>{{ text [1] uppercase  | slice: 0:5 }}</p>

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

A|

B:

D,

Attempts:

3 left

💡 Hint

Common Mistakes

Missing pipe symbol between pipes or wrong parameter separator.

Use | to chain pipes and : to pass arguments to pipes.

Practice

1. Why are pipes used in Angular templates?

easy

A. To format data for display without changing the original data

B. To create new components dynamically

C. To handle user input events

D. To manage application routing

Solution

1. Step 1: Understand the role of pipes in Angular

   Pipes transform data in templates to make it easier to read or display, like formatting dates or numbers.

2. Step 2: Identify what pipes do not do

   Pipes do not create components, handle events, or manage routing; these are handled by other Angular features.

3. Final Answer:

   To format data for display without changing the original data -> Option A

4. Quick Check:

   Purpose of pipes = format data display [OK]

Hint: Pipes format data visually, not logic or structure [OK]

Common Mistakes:

• Confusing pipes with event handlers
• Thinking pipes create components
• Assuming pipes change original data

2. Which of the following is the correct syntax to use a built-in pipe in Angular to format a date in a template?

easy

A. {{ today | date:'shortDate' }}

B. {{ today : date('shortDate') }}

C. {{ date(today, 'shortDate') }}

D. {{ today | formatDate:'shortDate' }}

Solution

1. Step 1: Recall Angular pipe syntax

   Angular pipes use the | symbol followed by the pipe name and optional parameters inside single quotes.

2. Step 2: Check each option's syntax

   {{ today | date:'shortDate' }} correctly uses {{ today | date:'shortDate' }}. Others misuse colon or function call syntax.

3. Final Answer:

   <code>{{ today | date:'shortDate' }}</code> -> Option A

4. Quick Check:

   Pipe syntax = {{ value | pipeName:'param' }} [OK]

Hint: Remember: pipes use | symbol, not colon or function calls [OK]

Common Mistakes:

• Using colon instead of pipe symbol
• Calling pipes like functions
• Misplacing quotes around parameters

3. Given the Angular template code:
{{ 1234.5678 | number:'1.2-2' }}
What will be the displayed output?

medium

A. 1234.57

B. 1,234.57

C. 1234.5678

D. 1,234.5678

Solution

1. Step 1: Understand the number pipe format

   The format '1.2-2' means minimum 1 digit before decimal, minimum 2 and maximum 2 digits after decimal, with thousands separator.

2. Step 2: Apply formatting to 1234.5678

   The number rounds to two decimals: 1234.57, and adds comma as thousands separator: 1,234.57.

3. Final Answer:

   1,234.57 -> Option B

4. Quick Check:

   Number pipe rounds and adds commas [OK]

Hint: Number pipe adds commas and rounds decimals [OK]

Common Mistakes:

• Ignoring thousands separator
• Not rounding decimals
• Confusing pipe parameter format

4. What is wrong with this Angular template code?
{{ user.birthdate | date:shortDate }}

medium

A. The variable name cannot have a dot

B. The pipe symbol should be a colon

C. The pipe parameter should be a string in quotes

D. The date pipe cannot format birthdate

Solution

1. Step 1: Check pipe parameter syntax

   Pipe parameters must be strings in single or double quotes, so shortDate should be 'shortDate'.

2. Step 2: Verify other parts

   The pipe symbol is correct, variable names can have dots for properties, and date pipe can format dates.

3. Final Answer:

   The pipe parameter should be a string in quotes -> Option C

4. Quick Check:

   Pipe parameters need quotes [OK]

Hint: Always quote pipe parameters like 'shortDate' [OK]

Common Mistakes:

• Omitting quotes around pipe parameters
• Replacing pipe symbol with colon
• Misunderstanding variable property access

5. You want to display a user's full name in uppercase and the registration date in a short date format in your Angular template. Which of the following is the correct way to use pipes together?

hard

A. {{ (user.fullName | uppercase) + ' - ' + (user.registrationDate | date:shortDate) }}

B. {{ user.fullName | uppercase | date:'shortDate' }}

C. {{ user.fullName + ' - ' + user.registrationDate | uppercase | date:'shortDate' }}

D. {{ user.fullName | uppercase }} - {{ user.registrationDate | date:'shortDate' }}

Solution

1. Step 1: Understand pipe usage on separate values

   Each value needs its own pipe usage; pipes cannot chain across different data types directly.

2. Step 2: Evaluate each option

   {{ user.fullName | uppercase }} - {{ user.registrationDate | date:'shortDate' }} correctly applies uppercase to the name and date to the date separately. {{ user.fullName | uppercase | date:'shortDate' }} chains incompatible pipes on one value. {{ user.fullName + ' - ' + user.registrationDate | uppercase | date:'shortDate' }} misuses concatenation with pipes. {{ (user.fullName | uppercase) + ' - ' + (user.registrationDate | date:shortDate) }} omits quotes around the pipe parameter shortDate.

3. Final Answer:

   <code>{{ user.fullName | uppercase }} - {{ user.registrationDate | date:'shortDate' }}</code> -> Option D

4. Quick Check:

   Use separate pipes for separate values [OK]

Hint: Apply pipes separately to each value, not chained across different types [OK]

Common Mistakes:

• Chaining pipes on incompatible data
• Trying to concatenate inside pipe expressions
• Using parentheses for expressions in templates