Notes on RESTful APIs and Building with Express.js

Introduction to APIs

• API Definition: Application Programming Interface, a method for computers to communicate.
• Interaction with API: Similar to using a website, but requests are coded.
  • Example: Use NASA's REST API to request JSON data on asteroids.

RESTful APIs

• REST: Representational State Transfer, the standard for API development since early 2000s.
• Resources: Organized into URIs (Uniform Resource Identifiers).
• HTTP Requests:
  • GET: Read data
  • POST: Create new resource
  • PATCH: Update resource
  • DELETE: Remove resource
• Request Format:
  • Start line with HTTP verb and URI
  • Headers (e.g., Accept, Authorization)
  • Body with custom data payload
• Response Format:
  • Status code (200s: success, 400s: client error, 500s: server error)
  • Headers with response information
  • Body usually in JSON
• Stateless Architecture: Every request/response is independent.

Building a RESTful API with Express.js

• Express.js: Popular framework for building RESTful APIs in Node.js.
• Setup:
  • Use VS Code, have Node.js installed (version 12 used).
  • Run npm init -y to create package.json.
  • Install Express with npm install express.
  • Create index.js file.
• Basic API Structure:
  • Import Express and initialize: const app = require('express')().
  • Listen on port: app.listen(8080).
  • Check API in browser or use tools like Insomnia or Postman.

Creating API Endpoints

• GET Request:
  • Create endpoint: app.get('/t-shirt', callbackFunction).
  • Handle request with req and send response with res.
• POST Request:
  • Dynamic URL parameter for unique resource ID.
  • Use req.params for URL parameters and req.body for request body.
  • Setup middleware to parse JSON: app.use(express.json()).
  • Check for required data (e.g., logo) and respond accordingly.

Error Handling and Response

• Use status codes (e.g., 200 for success, 418 for error with missing data).
• Test API with Insomnia: check requests and responses.

OpenAPI Specification

• Purpose: Standard to describe APIs in YAML.
• Benefits:
  • Fully document APIs for easy use.
  • Generate client/server-side code automatically.
  • Compatible with tools like AWS API Gateway for security and monitoring.
• Tools: Swagger Hub for code generation and documentation.

Conclusion

• RESTful APIs are essential for building reliable web applications.
• Express.js offers a minimal and effective framework for API development in Node.js.
• OpenAPI enhances API documentation and integration capabilities.

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Consider exploring more advanced content and tutorials on building APIs using the OpenAPI spec and cloud services.