Create Your Own API

Before You Study (5 mins)

Lesson focus: Until now, you've been a consumer of APIs (ordering food). Today, you become the chef (making food). You will build the endpoints that your game talks to.

What you should have ready:

• Your running server.js (Backend)
• Postman (optional) or just your browser

Quick Concepts

Think About

Before studying, consider:

1. What does your game need to send to save a score? (Name + Score).
2. What does your game need to receive to show the leaderboard? (List of Names + Scores).

By the End

After this lesson, you'll:

• ✅ Create a GET endpoint (to fetch scores)
• ✅ Create a POST endpoint (to save scores)
• ✅ Test your own API!

Order up! You're cooking now! 👨‍🍳

What We Learned

• Express.js: Makes creating a server as easy as 5 lines of code.
• GET /scores: A route that returns the list of high scores.
• POST /scores: A route that accepts a new score and adds it to the list.
• app.listen: Tells the server to start listening for requests.

Key Code Snippet

const express = require('express');
const app = express();

// The "Chef" serving the list of scores
app.get('/scores', (req, res) => {
  res.json([{ name: "Divyanshu", score: 100 }]);
});

app.listen(3000);

Checklist

• I installed express
• I created a GET route
• I visited localhost:3000/scores in my browser
• I saw JSON data appear!

Quick Quiz

Q1: What library makes building APIs easy?

• A) Depress.js
• B) Express.js ✓
• C) Impress.js

Q2: If you want to send data to the server, which method do you use?

• A) GET
• B) POST ✓
• C) STOP

Q3: What is req?

• A) Requirement
• B) Request (what the user sent) ✓
• C) Requisition

Bonus Challenge

Create a new route called /hello that returns {"message": "Hello World"}.

Next Lesson

Lesson 14: Where Instagram Stores 2 Billion Photos

You'll learn: Right now, if you restart the server, the scores disappear. We need a Database.

You built your own API! 🌐