NestJS : Interceptors

NestJS is a powerful framework for building scalable server-side applications with Node.js. If you’re new to NestJS or coding in general, you might be looking for ways to add extra functionality to your application without cluttering your core logic. One of the versatile tools that NestJS provides for this purpose is the Interceptor. This guide will walk you through what Interceptors are, how they work, and how you can use them to enhance your application with practical examples.

What is Interceptor?

In NestJS, an Interceptor acts as a middleman that can modify, enhance, or handle requests and responses. Here’s a simple way to think about it:

• Before the request reaches your controller methods: Interceptors can check or modify the request data.
• After the controller methods have processed the request: Interceptors can alter the response data or handle any exceptions.

Basic Structure of an Interceptor

To create an Interceptor in NestJS, you need to implement the NestInterceptor interface. This interface has one required method: intercept. An interceptor can be applied on various levels like Controller, Service, Method, and Global.

Here’s the basic structure

import { Injectable, NestInterceptor…