Project: A Notes API

This project combines Express, the filesystem, async errors and REST design into one small service you can run and test.

Project Structure

Keep the server entry, routes and storage in separate files. A small structure now saves confusion later.

notes-api/
  app.js
  routes/notes.js
  store.js
  data/notes.json

Storage

Write a small store module that reads and writes the JSON file. Serialise writes so two requests cannot corrupt the file.

import { readFile, writeFile } from "node:fs/promises";

const file = "data/notes.json";

export async function readNotes() {
  try {
    return JSON.parse(await readFile(file, "utf8"));
  } catch (error) {
    if (error.code === "ENOENT") return [];
    throw error;
  }
}

export async function saveNotes(notes) {
  await writeFile(file, JSON.stringify(notes, null, 2));
}

Routes

Provide GET /notes, POST /notes, PUT /notes/:id and DELETE /notes/:id. Validate a non-empty title and return 404 for missing ids.

Test the Edges

Try an empty title, a missing id, a malformed JSON body and a second server instance. Each should produce a clear response rather than a crash.

Practice

1. Add a createdAt timestamp to each note.
2. Add a query parameter to filter notes by a search word.
3. Return the total count in a header or a wrapper object.

Hands-on exercise

Build the notes API.
1. GET /notes returns all notes.
2. POST /notes creates a note with a title and body.
3. DELETE /notes/:id removes one note.
4. Missing ids return 404 and empty titles return 422.

Recap

A finished API separates routes and storage, validates input, persists data and handles every error path.