Axios setup and configuration in Vue - Performance & Optimization

Performance: Axios setup and configuration

MEDIUM IMPACT

This affects page load speed and interaction responsiveness by controlling how HTTP requests are made and managed in the app.

Making HTTP requests in a Vue app

Vue

import axios from 'axios';

const apiClient = axios.create({
  baseURL: 'https://api.example.com',
  timeout: 5000
});

export default {
  data() {
    return { data: null };
  },
  methods: {
    async fetchData() {
      const response = await apiClient.get('/data');
      this.data = response.data;
    }
  }
}

Using a single configured Axios instance reduces repeated setup and allows centralized control of requests.

📈 Performance GainSaves bundle size and reduces network setup overhead improving interaction responsiveness

Making HTTP requests in a Vue app

Vue

import axios from 'axios';

export default {
  data() {
    return { data: null };
  },
  methods: {
    fetchData() {
      axios.get('https://api.example.com/data')
        .then(response => {
          this.data = response.data;
        });
    }
  }
}

Creating a new Axios instance or importing axios directly everywhere causes repeated setup and larger bundle size.

📉 Performance CostAdds unnecessary bundle size and can cause repeated network setup overhead

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Direct axios calls everywhere	Minimal	0	0	[!] OK
Single configured axios instance	Minimal	0	0	[OK] Good

Rendering Pipeline

Axios setup affects the network request phase before rendering. Efficient setup avoids blocking UI updates waiting for data.

→Network

→JavaScript Execution

→Rendering

⚠️ BottleneckNetwork latency and blocking JavaScript execution during request handling

Core Web Vital Affected

INP

This affects page load speed and interaction responsiveness by controlling how HTTP requests are made and managed in the app.

Optimization Tips

1Use a single Axios instance to avoid repeated setup overhead.

2Configure timeouts to prevent hanging requests blocking UI.

3Centralize request configuration to reduce bundle size and improve maintainability.

Performance Quiz - 3 Questions

What is a performance benefit of using a single Axios instance in a Vue app?

A Blocks rendering until all requests finish

B Reduces repeated setup and network overhead

C Increases bundle size by duplicating code

D Automatically caches all responses

DevTools: Network

How to check: Open DevTools, go to Network tab, filter XHR requests, and observe request timing and size.

What to look for: Look for repeated or slow requests and large payloads that delay interaction responsiveness.

Practice

1. What is the main purpose of using axios.create() in a Vue project?

easy

A. To convert Axios requests into Vue components

B. To automatically fetch data when the component mounts

C. To create a reusable Axios client with custom settings

D. To replace Vue's reactive system with Axios

Solution

1. Step 1: Understand axios.create()

   This method creates a new Axios instance that can have its own configuration like baseURL, headers, and timeout.

2. Step 2: Purpose in Vue projects

   Using axios.create() helps keep your API calls consistent and reusable across components by sharing the same settings.

3. Final Answer:

   To create a reusable Axios client with custom settings -> Option C

4. Quick Check:

   axios.create() = reusable client [OK]

Hint: Remember axios.create() makes a custom client [OK]

Common Mistakes:

• Thinking axios.create() fetches data automatically
• Confusing axios.create() with Vue lifecycle hooks
• Assuming axios.create() changes Vue's reactivity

2. Which of the following is the correct way to set a base URL when creating an Axios instance?

easy

A. const api = axios.create('https://api.example.com')

B. const api = axios.create(baseURL = 'https://api.example.com')

C. const api = axios.create({ url: 'https://api.example.com' })

D. const api = axios.create({ baseURL: 'https://api.example.com' })

Solution

1. Step 1: Check axios.create() syntax

   axios.create() accepts an object with configuration keys like baseURL, timeout, and headers.

2. Step 2: Identify correct baseURL usage

   The correct key for setting the base URL is baseURL inside the config object.

3. Final Answer:

   const api = axios.create({ baseURL: 'https://api.example.com' }) -> Option D

4. Quick Check:

   baseURL inside object = const api = axios.create({ baseURL: 'https://api.example.com' }) [OK]

Hint: Use an object with baseURL key inside axios.create() [OK]

Common Mistakes:

• Passing baseURL as a separate argument
• Using url instead of baseURL
• Passing a string directly without an object

3. Given this Axios instance setup in a Vue component:

const api = axios.create({ baseURL: 'https://api.example.com', timeout: 1000 });

api.get('/users')
  .then(response => console.log(response.data))
  .catch(error => console.log('Error:', error.message));

What will happen if the server takes 2 seconds to respond?

medium

A. The request will timeout and log an error message

B. The request will succeed and log the user data

C. The request will retry automatically until success

D. The request will hang indefinitely without error

Solution

1. Step 1: Understand timeout setting

   The timeout is set to 1000 milliseconds (1 second), so if the server takes longer, Axios will abort the request.

2. Step 2: Effect on slow response

   Since the server takes 2 seconds, which is longer than 1 second, Axios triggers a timeout error and the catch block runs.

3. Final Answer:

   The request will timeout and log an error message -> Option A

4. Quick Check:

   Timeout 1s > 2s response = error [OK]

Hint: Timeout shorter than response time causes error [OK]

Common Mistakes:

• Assuming Axios retries automatically
• Thinking the request will succeed despite timeout
• Ignoring the catch block handling

4. Identify the error in this Axios setup code inside a Vue component:

const api = axios.create({
  baseURL: 'https://api.example.com',
  timeout: '5000',
  headers: { 'Content-Type': 'application/json' }
});

medium

A. timeout should be a number, not a string

B. baseURL must be inside headers object

C. Content-Type header is invalid here

D. axios.create() cannot have headers property

Solution

1. Step 1: Check timeout data type

   Timeout expects a number representing milliseconds, but here it is a string '5000'.

2. Step 2: Validate other properties

   baseURL is correctly placed, and headers with Content-Type is valid for axios.create().

3. Final Answer:

   timeout should be a number, not a string -> Option A

4. Quick Check:

   timeout must be number, not string [OK]

Hint: Timeout must be numeric, not quoted string [OK]

Common Mistakes:

• Putting baseURL inside headers
• Removing headers property
• Using string for timeout value

5. You want to create an Axios instance in Vue that automatically adds an Authorization header with a token stored in localStorage for every request. Which setup is correct?

hard

A. const api = axios.create({ baseURL: 'https://api.example.com' }); api.defaults.headers.common['Authorization'] = `Bearer ${localStorage.getItem('token')}`;

B. const api = axios.create({ baseURL: 'https://api.example.com' }); api.interceptors.request.use(config => { config.headers.Authorization = `Bearer ${localStorage.getItem('token')}`; return config; });

C. const api = axios.create({ baseURL: 'https://api.example.com', headers: { Authorization: `Bearer ${localStorage.getItem('token')}` } });

D. const api = axios.create({ baseURL: 'https://api.example.com', headers: { Authorization: localStorage.token } });

Solution

1. Step 1: Understand token dynamic retrieval

   The token in localStorage can change, so it should be read fresh before each request, not just once at setup.

2. Step 2: Use Axios interceptor for dynamic headers

   Using an interceptor lets you add or update headers before every request, ensuring the latest token is used.

3. Step 3: Evaluate options

   const api = axios.create({ baseURL: 'https://api.example.com' }); api.interceptors.request.use(config => { config.headers.Authorization = `Bearer ${localStorage.getItem('token')}`; return config; }); uses an interceptor to set Authorization header dynamically. Options A and C set it once at creation, which may become stale. const api = axios.create({ baseURL: 'https://api.example.com', headers: { Authorization: localStorage.token } }); uses incorrect localStorage access.

4. Final Answer:

   Use an interceptor to add Authorization header dynamically before each request -> Option B

5. Quick Check:

   Interceptor for dynamic token = const api = axios.create({ baseURL: 'https://api.example.com' }); api.interceptors.request.use(config => { config.headers.Authorization = `Bearer ${localStorage.getItem('token')}`; return config; }); [OK]

Hint: Use request interceptor to add fresh token each time [OK]

Common Mistakes:

• Setting headers once at creation, ignoring token updates
• Accessing localStorage.token instead of getItem()
• Not returning config in interceptor