How to Use Axios Interceptors to Handle API Error Responses

When building modern web applications, handling API calls and their responses is a critical part of development. Axios, a popular JavaScript library, simplifies making HTTP requests, but it also comes with built-in features like interceptors that allow developers to manage responses and errors in a more streamlined and efficient manner.

In this article, we will focus on using Axios interceptors to handle API error responses effectively, allowing you to standardize error handling across your entire application.

What is Axios?

Axios is a promise-based HTTP client for JavaScript that supports the async/await syntax for making requests to APIs. It's popular because it's simple to use, and its capabilities can be easily extended with interceptors.

Axios Basics Example:

import axios from 'axios';

axios.get('/api/data')
  .then(response => {
    console.log(response.data);
  })
  .catch(error => {
    console.error('Error fetching data:', error);
  });

While this example demonstrates how to handle requests and errors with .then and .catch, using interceptors can make your code more efficient when you need to manage multiple API requests.

What are Axios Interceptors?

Axios interceptors are functions that allow you to intercept and handle both requests and responses before they are processed by .then or .catch. This is particularly useful when you need to apply common configurations to all requests or handle error responses in a uniform way.

There are two main types of interceptors:

1. Request Interceptor: Used to modify or add headers, tokens, or other configurations to requests before they are sent.
2. Response Interceptor: Used to handle responses or errors globally, including logging or retrying requests when necessary.

Why Use Response Interceptors?

When dealing with multiple API endpoints, each may return different types of error messages or status codes. Without interceptors, you would need to handle errors for each individual API call, which can lead to repetitive and unmaintainable code.

With a response interceptor, you can manage all error responses in a single place, ensuring a consistent approach to handling errors across your app.

Setting Up an Axios Response Interceptor

1. Install Axios

First, make sure you have Axios installed in your project:

npm install axios

2. Create an Axios Instance

To set up interceptors, it's best to create an Axios instance that can be reused throughout your app. This helps to standardize your request and response handling.

import axios from 'axios';

axios.get('/api/data')
  .then(response => {
    console.log(response.data);
  })
  .catch(error => {
    console.error('Error fetching data:', error);
  });

3. Add a Response Interceptor

You can add a response interceptor to catch and handle errors before they reach your .then or .catch blocks in your individual API calls.

npm install axios

4. Making API Calls

With the interceptor in place, you can now use apiClient for your API calls. If any error occurs, it will be automatically caught and handled by the interceptor.

import axios from 'axios';

const apiClient = axios.create({
  baseURL: 'https://api.example.com',  // Replace with your API base URL
  headers: {
    'Content-Type': 'application/json',
    Accept: 'application/json',
  },
});

In this setup, you don't need to write error-handling code for every single API call. The interceptor centralizes this logic and makes your API calls cleaner and easier to maintain.

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Practical Use Cases for Axios Interceptors

1. Automatic Token Refresh

If your API uses authentication tokens (e.g., JWT), you may encounter a situation where the token expires, and you need to refresh it. Axios interceptors can be used to automatically refresh the token when a 401 Unauthorized response is received.

apiClient.interceptors.response.use(
  (response) => {
    // If the response is successful (status code 2xx), return the response data
    return response;
  },
  (error) => {
    // Handle errors globally
    if (error.response) {
      // Server responded with a status code out of 2xx range
      const statusCode = error.response.status;
      const errorMessage = error.response.data.message || 'An error occurred';

      // Handle different status codes accordingly
      if (statusCode === 401) {
        // Handle unauthorized error, for example by redirecting to login
        console.error('Unauthorized access - redirecting to login');
      } else if (statusCode === 500) {
        // Handle server errors
        console.error('Server error - try again later');
      } else {
        // Handle other types of errors
        console.error(`Error ${statusCode}: ${errorMessage}`);
      }
    } else if (error.request) {
      // No response received (network error, timeout, etc.)
      console.error('Network error - check your internet connection');
    } else {
      // Something else happened during the request
      console.error('Request error:', error.message);
    }

    // Optionally, return a rejected promise to ensure `.catch` is triggered in individual requests
    return Promise.reject(error);
  }
);

2. Handling Network Errors

If your app relies on external APIs, network issues can be a common problem. Axios interceptors can help provide user-friendly error messages in case of network failures.

// Example API call
apiClient.get('/users')
  .then(response => {
    console.log('User data:', response.data);
  })
  .catch(error => {
    // This will be triggered if the error isn't handled by the interceptor
    console.error('Error fetching users:', error);
  });

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Benefits of Using Axios Interceptors

1. Centralized Error Handling: Instead of writing error-handling code for every API call, you can handle errors in a single place.

2. Cleaner Code: Since error handling is taken care of by the interceptor, your individual API calls will be cleaner and more concise.

3. Improved Maintainability: Changes to error handling (e.g., adding new cases or refining error messages) can be done in one place, making the codebase easier to maintain.

4. Consistency: Interceptors ensure a consistent approach to handling errors, so you don’t have to worry about missing edge cases or writing redundant code.

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Conclusion

Using Axios interceptors for handling API error responses can greatly improve the structure, maintainability, and consistency of your code. By centralizing the error handling logic, you can make your API calls more efficient and reduce repetitive code across your application.

Interceptors are a powerful feature of Axios that can be used for a wide range of use cases, from managing token refreshes to displaying user-friendly error messages during network failures. Start leveraging Axios interceptors today to simplify error handling and improve your application's resilience!

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