Building a REST API with Express

// routes/todos.js — Full CRUD REST API
const express = require('express');
const router  = express.Router();

let todos  = [];
let nextId = 1;

// GET /todos — list all (with optional ?done= filter)
router.get('/', (req, res) => {
    const { done } = req.query;
    const result = done !== undefined
        ? todos.filter(t => t.done === (done === 'true'))
        : todos;
    res.json({ data: result, total: result.length });
});

// GET /todos/:id — get one
router.get('/:id', (req, res) => {
    const todo = todos.find(t => t.id === parseInt(req.params.id));
    if (!todo) return res.status(404).json({ error: 'Not found' });
    res.json({ data: todo });
});

// POST /todos — create
router.post('/', (req, res) => {
    const { title } = req.body;
    if (!title?.trim()) return res.status(400).json({ error: 'title is required' });
    const todo = { id: nextId++, title: title.trim(), done: false, createdAt: new Date() };
    todos.push(todo);
    res.status(201).json({ data: todo });
});

// PATCH /todos/:id — partial update
router.patch('/:id', (req, res) => {
    const todo = todos.find(t => t.id === parseInt(req.params.id));
    if (!todo) return res.status(404).json({ error: 'Not found' });
    if (req.body.title !== undefined) todo.title = req.body.title;
    if (req.body.done  !== undefined) todo.done  = Boolean(req.body.done);
    res.json({ data: todo });
});

// DELETE /todos/:id — delete
router.delete('/:id', (req, res) => {
    const idx = todos.findIndex(t => t.id === parseInt(req.params.id));
    if (idx === -1) return res.status(404).json({ error: 'Not found' });
    todos.splice(idx, 1);
    res.status(204).send();
});

module.exports = router;