Setting headers and params in Angular - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the HttpHeaders class.

Angular

import { HttpClient, [1] } from '@angular/common/http';

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

AHttpHeaders

BHttpResponse

CHttpRequest

DHttpParams

Attempts:

3 left

💡 Hint

Common Mistakes

Importing HttpParams instead of HttpHeaders.

Forgetting to import HttpHeaders at all.

The HttpHeaders class is imported from @angular/common/http to set HTTP headers.

2fill in blank

medium

Complete the code to create a new HttpHeaders object with a custom header.

Angular

const headers = new HttpHeaders().set('[1]', 'application/json');

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AContent-Type

BAuthorization

CAccept

DCache-Control

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Authorization' when no token is needed.

Using 'Accept' instead of 'Content-Type'.

The Content-Type header tells the server the format of the data sent.

3fill in blank

hard

Fix the error in setting multiple HTTP params.

Angular

const params = new HttpParams().[1]('page', '1').append('limit', '10');

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Aset

Bappend

Cadd

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'set' twice, which overwrites the first param.

Using non-existent methods like 'add' or 'push'.

The append method adds a new value without replacing existing ones, allowing chaining.

4fill in blank

hard

Fill both blanks to create headers and params for an HTTP GET request.

Angular

this.http.get(url, { headers: new HttpHeaders().[1]('Authorization', 'Bearer token'), params: new HttpParams().[2]('search', 'angular') });

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

Aset

Bappend

Cpush

Dadd

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'push' or 'add' which are not valid methods.

Using 'append' for headers which may cause unexpected behavior.

Use set to set the Authorization header and append to add a search param.

5fill in blank

hard

Fill all three blanks to create headers and params with multiple values.

Angular

const headers = new HttpHeaders().[1]('Accept', 'application/json');
const params = new HttpParams().[2]('page', '2').[3]('limit', '20');

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

Aset

Bappend

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'set' twice on params which overwrites previous values.

Using invalid methods like 'push' or 'add'.

Headers use set to assign 'Accept'. Params use append twice to add 'page' and 'limit'.

Practice

1. What is the main purpose of setting headers in an Angular HTTP request?

easy

A. To change the URL of the request

B. To add extra information like authentication tokens or content type

C. To modify the HTTP method (GET, POST, etc.)

D. To handle the response data format

Solution

1. Step 1: Understand what headers do

   Headers carry extra info like tokens or content type in HTTP requests.

2. Step 2: Compare options

   Only To add extra information like authentication tokens or content type correctly describes headers' purpose; others describe different concepts.

3. Final Answer:

   To add extra information like authentication tokens or content type -> Option B

4. Quick Check:

   Headers add info = A [OK]

Hint: Headers carry extra info like tokens, not URL or method [OK]

Common Mistakes:

• Confusing headers with URL parameters
• Thinking headers change HTTP method
• Assuming headers handle response data

2. Which of the following is the correct way to add a header named Authorization with value Bearer token123 using Angular's HttpHeaders?

easy

A. new HttpHeaders().set('Authorization', 'Bearer token123')

B. new HttpHeaders('Authorization', 'Bearer token123')

C. HttpHeaders.append('Authorization', 'Bearer token123')

D. HttpHeaders.add('Authorization', 'Bearer token123')

Solution

1. Step 1: Recall HttpHeaders usage

   HttpHeaders is immutable; use set method to add headers.

2. Step 2: Check each option

   Only new HttpHeaders().set('Authorization', 'Bearer token123') uses new HttpHeaders().set() correctly; others are invalid syntax or methods.

3. Final Answer:

   new HttpHeaders().set('Authorization', 'Bearer token123') -> Option A

4. Quick Check:

   Use set() on new HttpHeaders() = B [OK]

Hint: Use new HttpHeaders().set() to add headers [OK]

Common Mistakes:

• Trying to pass headers directly to constructor
• Using non-existent methods like append or add
• Not creating a new HttpHeaders instance first

3. Given the code below, what will be the final URL requested?

const params = new HttpParams().set('page', '2').set('sort', 'name');
this.http.get('/api/items', { params }).subscribe();

medium

A. /api/items

B. /api/items?sort=name&page=2

C. /api/items?page=2

D. /api/items?page=2&sort=name

Solution

1. Step 1: Understand HttpParams chaining

   Each set returns a new HttpParams with added param; chaining adds both params.

2. Step 2: Determine param order

   Params appear in order set: page=2 then sort=name.

3. Final Answer:

   /api/items?page=2&sort=name -> Option D

4. Quick Check:

   Params chained = URL with both params in order [OK]

Hint: Chained set() adds params in order to URL [OK]

Common Mistakes:

• Assuming only last set param remains
• Ignoring param order in URL
• Forgetting to pass params in request options

4. Identify the error in this Angular HTTP request code:

const headers = new HttpHeaders();
headers.set('Content-Type', 'application/json');
this.http.post('/api/data', body, { headers }).subscribe();

medium

A. Headers must be plain object, not HttpHeaders instance

B. Missing import for HttpHeaders

C. HttpHeaders is immutable; set() does not change original headers

D. post() method requires params object

Solution

1. Step 1: Understand HttpHeaders immutability

   HttpHeaders methods like set return new instances; original is unchanged.

2. Step 2: Analyze code behavior

   Headers remain empty because set result is not assigned back.

3. Final Answer:

   HttpHeaders is immutable; set() does not change original headers -> Option C

4. Quick Check:

   HttpHeaders immutable = assign set() result [OK]

Hint: Assign set() result to headers variable [OK]

Common Mistakes:

• Not assigning set() result back
• Assuming headers object changes in place
• Confusing HttpHeaders with plain objects

5. You want to send a GET request with headers { 'Authorization': 'Bearer abc123' } and query params { 'filter': 'active', 'limit': '10' }. Which code correctly sets both headers and params in Angular?

hard

A. const headers = new HttpHeaders({ Authorization: 'Bearer abc123' });
const params = new HttpParams({ fromObject: { filter: 'active', limit: '10' } });
this.http.get('/api/users', { headers, params }).subscribe();

B. const headers = new HttpHeaders('Authorization', 'Bearer abc123');
const params = { filter: 'active', limit: '10' };
this.http.get('/api/users', { headers, params }).subscribe();

C. const headers = new HttpHeaders();
headers.set('Authorization', 'Bearer abc123');
const params = new HttpParams().set('filter', 'active').set('limit', '10');
this.http.get('/api/users', { headers, params }).subscribe();

D. const headers = new HttpHeaders().add('Authorization', 'Bearer abc123');
const params = new HttpParams().add('filter', 'active').add('limit', '10');
this.http.get('/api/users', { headers, params }).subscribe();

Solution

1. Step 1: Check header creation

   HttpHeaders constructor accepts a plain object like { Authorization: 'Bearer abc123' } for initial headers.

2. Step 2: Check params creation

   HttpParams constructor accepts { fromObject: { filter: 'active', limit: '10' } } to set multiple params at once.

3. Step 3: Verify request call

   Both headers and params are passed correctly in the request options { headers, params }.

4. Final Answer:

   Use HttpHeaders({ Authorization: 'Bearer abc123' }) and HttpParams({ fromObject: { filter: 'active', limit: '10' } }) -> Option A

5. Quick Check:

   Use constructors with objects for headers and params = C [OK]

Hint: Use HttpHeaders({}) and HttpParams({fromObject:{}}) for multiple values [OK]

Common Mistakes:

• Wrong constructor arguments or plain objects without proper instances
• Not assigning set() result due to immutability
• Using non-existent methods like add()