Simple JSON API with Express

app.js

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

let nextId = 1;
let todos = [];

function addTodo(text) {
  const id = nextId;
  todos = [...todos, {
    id,
    text,
    done: false
  }];
  nextId++;
  return id;
}

app.use(express.json());

app.get('/api/todos', (req, res) => res.status(200).json(todos));

app.post('/api/todo', (req, res, next) => {
  if (!req.body || !req.body.text) {
    return next({ status: 400, message: 'text field is required' });
  }
  const id = addTodo(req.body.text);
  res.status(200).json({ id, success: true });
});

app.get('/api/todo/:id', (req, res) => {
  const id = parseInt(req.params.id, 10);
  const result = todos.find(todo => todo.id === id);
  if (!result) {
    return next({ status: 404, message: 'not found' });
  }
  res.status(200).json(result);
});

app.put('/api/todo/:id', (req, res) => {
  const id = parseInt(req.params.id, 10);
  const todo = todos.find(todo => todo.id === id);
  if (!todo) {
    return next({ status: 404, message: 'not found' });
  }
  updatedTodo = Object.assign({}, todo, req.body);
  todos = todos.map(doc => {
    if (doc.id === id) {
      return updatedTodo;
    }
    return doc;
  });
  res.status(200).json({ success: true });
});

app.use((err, req, res, next) => {
  res.status(err.status).json(err);
});

app.listen(3000, () => console.log('Example app listening on port 3000!'))