Setting headers and params in Angular - Performance & Optimization

Performance: Setting headers and params

MEDIUM IMPACT

This affects the network request time and how quickly the browser can start processing data from the server.

Sending HTTP requests with headers and query parameters

Angular

const headers = new HttpHeaders().set('Authorization', 'Bearer token');
const params = new HttpParams().set('filter', 'all');
this.http.get('/api/data', { headers, params })

Only includes necessary headers and params, reducing request size and speeding up response.

📈 Performance GainSaves 1-2kb in request size, reduces network latency, improves LCP

Sending HTTP requests with headers and query parameters

Angular

this.http.get('/api/data', { headers: new HttpHeaders({ 'Authorization': 'Bearer token', 'X-Custom-Header': 'value', 'Unused-Header': 'remove' }), params: new HttpParams().set('filter', 'all').set('unused', 'remove') })

Sending unnecessary headers and params increases request size and processing time on server and client.

📉 Performance CostAdds 1-2kb to request size, increasing network latency and blocking rendering longer

Performance Comparison

Pattern	Request Size	Network Latency	Server Processing	Verdict
Unoptimized headers and params	Large (extra headers/params)	Higher due to size	Longer due to extra data	[X] Bad
Optimized headers and params	Minimal necessary data	Lower due to smaller size	Faster processing	[OK] Good

Rendering Pipeline

Headers and params affect the network request phase before rendering. Larger requests delay server response, which delays browser painting of content.

→Network Request

→Response Processing

→Paint

⚠️ BottleneckNetwork Request size and server processing time

Core Web Vital Affected

LCP

This affects the network request time and how quickly the browser can start processing data from the server.

Optimization Tips

1Only send headers that the server requires.

2Avoid sending unused query parameters.

3Keep request size small to improve loading speed.

Performance Quiz - 3 Questions

How does sending unnecessary headers affect page performance?

A It increases request size and delays server response

B It reduces server processing time

C It improves browser rendering speed

D It has no effect on performance

DevTools: Network

How to check: Open DevTools, go to Network tab, select the request, and inspect the Headers and Query String Parameters sections.

What to look for: Look for unnecessary headers or params increasing request size and causing longer wait times.

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()