Microservices are easy to build, test, and deploy, which has inspired a dramatic uptick in the number of enterprises using them. Amid this adoption, it’s increasingly critical for companies to find ways to accelerate API development and integration. Recently, Nest.js provided a framework for microservices integration. And, Nest.js follows an Angular architecture, familiar to most frontend developers, allowing quick creation of dynamic REST APIs. Nest.js includes several other valuable benefits that can accelerate API development for microservices.


1) Nest.js Documentation is Fast, Accurate, and Efficient

Documenting code is always challenging. Maintaining documentation outside of code is not ideal, because it is frequently out of sync, and the update lag can mean developers aren’t referencing the most-current information. Nest.js solves for this with built-in library generation, a fast, accurate, and efficient way to generate documentation while coding a Nest.js framework application.


Nest.js makes use of Comodoc, an open-source documentation tool, enabling it to generate documents in seconds (no server needed), use different themes, create documentation coverage reports, include search documentation capabilities, implement responsive design, and more.


As a modern JavaScript framework, Comodoc supports object-oriented concepts including class, inheritance, interfaces, etc. But how can it generate documentation from code? Developers start by defining function parameters using a decorator or interface. Comodoc then reads the defined interface and decorator, creating a tabular structure for input parameters. After the interface for a function’s output parameters are defined, Comodoc will link the appropriate interface for output parameters in the documentation. Comodoc has a search feature that helps a developer find anything in a document.


An overview of application module relationships.


Add a best practice for developers to make inline comments while writing code. Then, when defining an algorithm or a particular function, Comodoc will read the inline comments and convert it to a description of the function. Comodoc also uses defined decorators and interfaces for linking to appropriate file in documentation.


List of methods and detailed signature of methods


Comodoc provide report for documentation coverage. We can see documentation coverage project or file wise. Comodoc creates basic class dependency diagrams for any class or service. Any generated document can be deployed and accessed similar to a web application. For a team member to access a documentation file, simply share the URL.


Each document in the list shows the shareable URL, the Type and the Identifier.
Use the Search box in the left menu to search all documents.


2) Automatic Swagger Generation

While working on a large application, it is not easy to maintain a list of end points and signatures exposed through APIs. In large applications, there can be multiple versions of the same API end point. It is possible that each version could have different input and output parameters for the same end points, making documenting all possibilities very challenging.


Swagger is a way to document these relationships. An OpenAPI specification, it is language-agnostic and  an accepted interface description definition format to document RESTful APIs. Nest.js includes a solution to generate and document Swagger out of a developer’s code through the decorators. Nest.js provides a dedicated module that documents this specification by leveraging decorators to generate an OpenAPI specification. It supports different types of response codes, with no need to maintain a separate Swagger file and no additional code required for Swagger to be generated. This enables developers to execute and test APIs in real time from the Swagger UI.



3) Nest.js Builds Unit and End-to-End Test Cases

Automated testing is considered an essential part of software development, allowing developers to test code quickly and get instant feedback to meet quality and performance goals. Automation increases developer productivity and ensures that tests are run at critical development lifecycle junctures (e.g. source code control check-in, feature integration, and version release). There are various types of automated testing, including unit tests, end-to-end (E2E) tests, integration tests, and more.


Normally, developers write unit test cases to check that a particular function or class behaves properly with different input parameters. Quality teams write E2E test cases to check the complete flow of a particular function. NestJ.js automatically scaffolds default unit tests for components and E2E tests for applications.


The advantages of Nest.js creating test cases include:

  1. Enhanced reliability and increased confidence automating API end points
  2. Easier to identify errors that could not be identified during unit tests
  3. Easy to set as a task in the deployment pipeline
  4. Easy to configure for different environments


4) Easy Task Scheduling

Automation is a fundamental component of DevOps, and task scheduling can improve automation performance. Task scheduling includes scheduling arbitrary code (methods/functions) to execute at a fixed date/time, at recurring intervals, or once after a specified interval. This is normally handled by packages like cron at the OS level. Nest.js provides a schedule package that integrates with the popular Node.js node-cron library.


Nest.js supports scheduling task in different ways:

  1. Declarative cron jobs (Declare cron job like linux cron)
  2. Declarative timeouts (Called once after specified time)
  3. Declarative intervals (Called every interval as per specified time)


Nest.js promotes access to the lifecycle method of scheduled tasks and includes attaching custom methods for task scheduling. These features improve automation performance.


With the growing adoption of microservices, finding ways to accelerate API development is key. Nest.js offers a robust framework for REST API development that includes features to enhance speed and accuracy. From automatic test case creation and documentation to Swagger generation and task scheduling, Nest.js improves the API development workflow.


To implement Nest.js, please refer to this documentation.

Pinal Sakarvadia

Pinal Sakarvadia

Full Stack Developer, Architect

With more than 15 years of experience in various web technologies, Pinal is a full-stack developer, architect, and consultant. He helps customers and internal teams with best-of-breed architectures, insights on the use of various technologies, and prototype development. Pinal is very passionate about microservices, micro-frontends, cloud-native applications, and API-first development.

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