For building large-scale applications, people look for frameworks that are lightweight. For that reason, NestJS is taking command over ExpressJS. No doubt ExpressJS has gained popularity in the last few years among developers, NestJS is on the way and will pave the way to greater use in upcoming years. Now, when you don’t know about ExpressJS and NestJS, no worries. We’ll help you in grasping the best key features of it.

NestJS is a NodeJS framework that is used for building scalable server-side applications. With NestJS, you can have readable and predictable code, all thanks to TypeScript which makes it more popular. It is an extensible, progressive and versatile framework. In spite of API being stable in the case of ExpressJS, it cannot handle async/await functions. To avoid such issues, NestJS has taken place.

And, ExpressJS is a fast NodeJS framework used to build web and mobile applications.

Here are 5 differences between ExpressJS and NestJS That You Should Know:

1. Unopinionated and Opinionated

Since ExpressJS is unopinionated which means it doesn’t have a set of pre-defined rules to follow which gives developers the freedom to make multiple possibilities and implement code as per the need. While NestJS is opinionated which means it has SOLID Principles to follow which helps to avoid any issues during development time and also develops the application with less prone to error. NestJS is completely Angular-based thus it uses TypeScript as its primary language. Using TypeScript makes the application reliable and bug-free.

2. Model View Controller Pattern

NestJS follows the MVC (Model View Controller) architecture whereas ExpressJS does not. MVC is basically a software design pattern that is used to implement UI, controlling logic, and data. Since ExpressJS doesn’t follow MVC, there’s no proper structure which makes the application inefficient and less optimized. NestJS becomes a better choice for developers as it is clearly based on an architecture with components like modules, controllers, and providers. You can also divide the application into microservices which makes development easy and code understandable.

3. TypeScript and Decorators

NestJS supports TypeScript which is another boon to it. TypeScript follows static typing, is reliable, and also has a “type” feature. It is very beneficial in the case of building large-scale efficient applications. NestJS is entirely written in TypeScript which is not the case with ExpressJS making ExpressJS less efficient and not also compatible to run on multiple browsers. TypeScript also has decorators as its feature. Decorators allow metaprogramming which allows programs to treat other programs as their data that eventually helps in designing a program to read, analyze, and generate other programs while running. You can also write custom decorator and use it in different parts of a project.

4. Easy Unit-Testing

NestJS CLI (Command Line Interface) comes with a default testing environment which is configured with Jest. When a service, interceptors, or controllers are generated, a “spec” file is created along with it by CLI which provides auto-generated testing bed code, so that developers don’t need to write extra code for the unit testing. Hence, Unit Testing happens to be much easier with NestJS which is not the case with ExpressJS. For performing unit testing in ExpressJS, a separate code is written which takes time and can also lower down application productivity rate.

5. Performance

NestJS incorporates a CLI (command-line interface) to boost productivity, CLI helps in giving commands directly for which you don’t need to write long codes. Dependency Injection is also the reason why developers choose NestJS because it allows you to add as many dependencies as possible for the smooth functioning of the application. NestJS has an out-of-the-box structure for many developers and allows third-party plugins. These are the reasons NestJS helps you in designing scalable applications which in return improves performance and brings an optimized solution.