Introduction to REST APIs With Express

An application programming interface, commonly referred to as an API, is a set of rules that allows software applications, such as clients and servers, to communicate with each other.

A framework is a tool that helps developers build reliable applications faster by providing a customizable blueprint that bundles the most frequently used functionalities for crafting a specific type of software, such as web servers.

Express is a Node.js framework that helps you implement HTTP APIs by turning your rules into real routes, requests, and responses.

Learning objectives

In this module, you'll learn how to craft production-ready APIs in Node.js using Express — a popular framework for building web applications in Node.js.

Among other things, this framework provides an intuitive routing mechanism for handling HTTP requests, follows the middleware architecture to easily extend its features, and makes it easy to serve static files and dynamic HTML pages.

After completing this module, you will be able to:

• Explain the client–server model and how web clients and servers communicate.
• Understand how HTTP requests and responses work, including methods, headers, and status codes.
• Explain what an API is and how an API acts as a contract between a client and a server.
• Design RESTful APIs with predictable, resource-oriented endpoints.
• Create and run an Express web server and implement routes for multiple HTTP methods.
• Process requests with middleware and build reusable request pipelines.
• Parse request data from route parameters, query parameters, headers, and body payloads.
• Validate inputs (params + body) and return consistent 4xx responses when the contract is not respected.
• Handle runtime errors centrally and return clean 5xx responses without crashing the server.
• Apply basic API protection with rate limiting strategies.
• Serve static assets and optionally render dynamic HTML using a template engine.