Axios interceptors in Vue - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a request interceptor to Axios.

Vue

axios.interceptors.request.use(function(config) {
  // Modify config here
  return [1];
});

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

Arequest

Bresponse

Cconfig

Derror

Attempts:

3 left

💡 Hint

Common Mistakes

Returning the response instead of config.

Not returning anything from the interceptor.

The request interceptor must return the config object to continue the request.

2fill in blank

medium

Complete the code to add a response interceptor that handles errors.

Vue

axios.interceptors.response.use(function(response) {
  return response;
}, function([1]) {
  // Handle error
  return Promise.reject(error);
});

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

Aerror

Bresponse

Cconfig

Drequest

Attempts:

3 left

💡 Hint

Common Mistakes

Using response instead of error in the error handler.

Not returning Promise.reject(error) to propagate the error.

The error handler function receives the error object.

3fill in blank

hard

Fix the error in the interceptor code to correctly add an Authorization header.

Vue

axios.interceptors.request.use(function(config) {
  config.headers.Authorization = 'Bearer ' + [1];
  return config;
});

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

Aresponse

Btoken

Cerror

Dconfig

Attempts:

3 left

💡 Hint

Common Mistakes

Using config or response instead of the token string.

Forgetting to concatenate 'Bearer ' before the token.

The token variable holds the authorization token string to add to headers.

4fill in blank

hard

Fill both blanks to create an interceptor that logs the URL and method of each request.

Vue

axios.interceptors.request.use(function(config) {
  console.log('Request:', config.[1], config.[2]);
  return config;
});

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

Aurl

Bmethod

Cdata

Dheaders

Attempts:

3 left

💡 Hint

Common Mistakes

Using data or headers instead of url or method.

Logging undefined properties.

The config.url and config.method properties hold the request URL and HTTP method.

5fill in blank

hard

Fill all three blanks to create a response interceptor that extracts data and handles errors with a custom message.

Vue

axios.interceptors.response.use(function([1]) {
  return response.[2];
}, function(error) {
  console.error('Request failed:', error.[3]);
  return Promise.reject(error);
});

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

Aresponse

Bdata

Cmessage

Dconfig

Attempts:

3 left

💡 Hint

Common Mistakes

Not returning response.data but the whole response.

Logging error.config instead of error.message.

The response object is passed in, and its data property holds the server data. The error object has a message property describing the error.

Practice

1. What is the main purpose of Axios interceptors in a Vue application?

easy

A. To modify requests or responses globally before they reach your components

B. To create new Axios instances for each API call

C. To replace Vue lifecycle hooks with Axios methods

D. To automatically refresh the Vue component state

Solution

1. Step 1: Understand Axios interceptors role

   Axios interceptors allow you to intercept and modify requests or responses globally before they reach your Vue components.

2. Step 2: Compare options

   Options B, C, and D describe unrelated or incorrect uses of Axios interceptors.

3. Final Answer:

   To modify requests or responses globally before they reach your components -> Option A

4. Quick Check:

   Interceptor purpose = Modify requests/responses globally [OK]

Hint: Interceptors act like global filters for requests and responses [OK]

Common Mistakes:

• Thinking interceptors create new Axios instances
• Confusing interceptors with Vue lifecycle hooks
• Assuming interceptors update component state automatically

2. Which of the following is the correct syntax to add a request interceptor using Axios in Vue?

easy

A. axios.use.interceptors.request(config => { return config })

B. axios.request.interceptors.use(config => { return config })

C. axios.interceptors.request.use(config => { return config })

D. axios.interceptors.use.request(config => { return config })

Solution

1. Step 1: Recall Axios interceptor syntax

   The correct syntax to add a request interceptor is axios.interceptors.request.use(callback).

2. Step 2: Identify correct option

   Only axios.interceptors.request.use(config => { return config }) matches the correct syntax; others have incorrect property order or method calls.

3. Final Answer:

   axios.interceptors.request.use(config => { return config }) -> Option C

4. Quick Check:

   Correct syntax = axios.interceptors.request.use [OK]

Hint: Remember: interceptors.request.use is the correct chain [OK]

Common Mistakes:

• Swapping 'request' and 'interceptors' order
• Using 'use' before 'interceptors'
• Missing the return of config in the callback

3. Given this Axios response interceptor code in Vue:

axios.interceptors.response.use(response => {
  response.data.modified = true;
  return response;
});

const result = await axios.get('/api/data');
console.log(result.data.modified);

What will be logged to the console?

medium

A. undefined

B. true

C. false

D. An error will occur

Solution

1. Step 1: Analyze the response interceptor

   The interceptor adds a property 'modified' with value true to response.data before returning it.

2. Step 2: Understand the logged value

   After the GET request, result.data.modified will be true because the interceptor modified it.

3. Final Answer:

   true -> Option B

4. Quick Check:

   Interceptor modifies data = logged true [OK]

Hint: Interceptors can add properties to response data before use [OK]

Common Mistakes:

• Assuming interceptor does not modify response
• Expecting undefined because property was added dynamically
• Thinking an error occurs due to property addition

4. Identify the error in this Vue Axios interceptor code:

axios.interceptors.request.use(config => {
  config.headers['Authorization'] = 'Bearer token';
});

medium

A. Missing return of config in the interceptor callback

B. Headers should be set on response, not config

C. Authorization header value must be a function

D. Interceptor should be added on axios.request, not axios.interceptors

Solution

1. Step 1: Check interceptor callback requirements

   Axios interceptors must return the config object after modifying it to continue the request chain.

2. Step 2: Identify missing return

   The code modifies headers but does not return config, causing the request to hang or fail.

3. Final Answer:

   Missing return of config in the interceptor callback -> Option A

4. Quick Check:

   Always return config in request interceptor [OK]

Hint: Always return config or response in interceptors [OK]

Common Mistakes:

• Forgetting to return config or response
• Setting headers on response instead of request config
• Misplacing interceptor on wrong Axios property

5. You want to globally handle 401 Unauthorized errors in your Vue app using Axios interceptors. Which approach correctly implements this behavior?

hard

A. Use a response interceptor to retry the request infinitely on 401 errors

B. Use a request interceptor to modify the request URL on 401 errors

C. Use a request interceptor to add a 401 status header before sending

D. Use a response interceptor to check error response status and redirect to login

Solution

1. Step 1: Understand 401 error handling

   401 Unauthorized errors come from server responses, so handling must be in a response interceptor.

2. Step 2: Choose correct handling method

   Use a response interceptor to check error response status and redirect to login correctly uses a response interceptor to detect 401 status and redirect user to login page.

3. Step 3: Eliminate incorrect options

   Retrying infinitely causes loops; using a request interceptor cannot handle response errors like 401; adding a 401 status header in the request is invalid.

4. Final Answer:

   Use a response interceptor to check error response status and redirect to login -> Option D

5. Quick Check:

   401 errors handled in response interceptor [OK]

Hint: Handle server errors in response interceptors, not request ones [OK]

Common Mistakes:

• Trying to handle response errors in request interceptors
• Retrying requests infinitely on 401 errors
• Adding fake status headers in requests