Building REST APIs with Node.js

A REST API exposes resources through predictable URLs and HTTP methods. For example, a users resource might support GET /users, GET /users/42, and POST /users.

The request lifecycle

When a request reaches a Node.js server, the application normally identifies the route, validates the input, performs the required work, and sends a response. Each step should have a clear responsibility so errors are easier to diagnose.

Responses should use meaningful status codes. A successful read commonly returns 200, a newly created resource returns 201, invalid input returns 400, and a missing resource returns 404.

Validate input at the boundary

Data received from a request should be treated as untrusted. Validate required fields, check types, and reject values that do not meet the API contract before passing them to business logic or a database.

Validation also makes the API easier to use. A response such as this gives a client enough information to correct its request:

{
  "error": "The email field must be a valid address."
}

Design for consistency

Use the same response structure and naming conventions across endpoints. Consistent APIs are easier to document, test, and consume. As the project grows, separate routing, validation, business logic, and data access instead of keeping everything in one request handler.