Understanding Request and Response Interceptors in JavaScript

As a developer, you may have come across the terms “request interceptor” and “response interceptor” while working with APIs in JavaScript.
In this blog post, we’ll explore what these terms mean and how they can be used to enhance your code. We’ll also explore a practical example of how to implement interceptors using JavaScript.

What are Request and Response Interceptors?

Request and response interceptors in the browser are functions that allow developers to modify or intercept network requests and responses that are being sent or received by the browser.

They allow you to modify the request or response before it is sent or received by the server.

Interceptors are useful because they allow developers to add custom functionality to requests and responses without modifying the actual code that makes the request. This means that developers can modify or enhance the behavior of an application without needing to modify the underlying code. Interceptors can also help to standardize the format of requests and responses, making it easier to work with data from multiple APIs or services.

Implementing Interceptors in JavaScript:

To implement request and response interceptors in JavaScript, we’ll use the Fetch API. Here’s a code snippet that demonstrates how to use interceptors with Fetch:

Let’s break down this code into its individual parts:

1. fetchRequestInterceptor: This function intercepts the request and modifies it by adding a default method of “GET” if one isn’t specified. It then returns the modified request.
2. fetchResponseInterceptor: This function intercepts the response and modifies it by checking the status code. If the status is 200, it converts the response to JSON format and returns it as an object with a “Success” message. If the status is not 200, it returns an object with a “Failed” message, a null data object, and the reason for the failure.
3. myFetch: This function wraps the Fetch API and applies the interceptors to the request and response. It returns the modified response object.
4. withSuccess and withFailure: These functions demonstrate how myFetch can be used to handle successful and failed requests.

Some common use cases for request and response interceptors include:

• Adding authentication tokens to requests
• Logging requests and responses for debugging purposes
• Handling errors from the server
• Standardizing response formats across multiple APIs or services
• Adding or removing headers from requests

Request and response interceptors are can be used to enhance your JavaScript code. By intercepting HTTP requests and responses, you can modify them to fit your specific needs.

In this blog post, we demonstrated how to implement interceptors using the Fetch API. We hope you found this example helpful and encourage you to explore how interceptors can be used to improve your own code.