Reading a Body

Part of the Express Basics section of Coddy's Node.js journey. Lesson 15 of 23.

A POST request sends data in its body, and Express does not read the body unless you ask it to.

app.use(express.json());

app.post('/api/loans', (req, res) => {
    const { bookId, member } = req.body;
    res.status(201).json({ bookId, member, due: '2026-11-08' });
});

GET asks for something; POST sends something to be created. express.json() is middleware that reads every JSON body into req.body. Without it req.body is undefined. A route that creates something answers 201 with what it made.

Check the body before you save it. A missing field is the client's mistake, so answer 400 and save nothing.

Challenge

Easy

Visitors can add their own recipes. A program sends the new recipe as JSON in the body of a POST request, and your API saves it.

In server.js, add express.json() with the other app.use lines, above the routes, so that a JSON body arrives in req.body.
Add a route for POST requests to /api/recipes. It reads title and tags from the body, for example {"title": "Miso Soup", "tags": ["vegan", "soup"]}.
It builds the new recipe with the next number id: the four recipes have ids 1 to 4, so the first new one gets 5. It keeps the title and tags it was sent. If no tags came, use an empty list, [].
It adds the recipe to the recipes array, so GET /api/recipes lists it. Then it responds with status 201 and the new recipe as JSON: {"id": 5, "title": "Miso Soup", "tags": ["vegan", "soup"]}
When the body has no title, it saves nothing and responds with status 400 and this JSON: {"error": "A recipe needs a title"}

Try it: Press Run. Pick POST in the method picker, type /api/recipes as the path, and put {"title": "Miso Soup", "tags": ["vegan", "soup"]} in the body box. You should see status 201 and the recipe with "id": 5. Pick GET and send /api/recipes: five recipes, with Miso Soup last. Then POST {"tags": ["dinner"]} to /api/recipes: status 400 and {"error":"A recipe needs a title"}. GET /api/recipes still lists five recipes.

Try it yourself

import { escapeHtml } from './html.js';
import express from 'express';
import { randomUUID } from 'node:crypto';
import { recipes } from './data.js';

const app = express();

app.use((req, res, next) => {
    console.log(`${req.method} ${req.url}`);
    next();
});

app.use((req, res, next) => {
    res.set('X-Request-Id', randomUUID());
    next();
});

app.use(express.static('public'));

app.get('/', (req, res) => {
    const items = recipes.map((r) => `<li><a href="/recipes/${r.id}">${escapeHtml(r.title)}</a></li>`);
    res.send(`<link rel="stylesheet" href="/style.css"><h1>Recipe Box</h1><ul>${items.join('')}</ul>`);
});

// type('text') sends plain text, so each title shows on its own line.
app.get('/recipes', (req, res) => {
    const { tag } = req.query;
    const list = tag ? recipes.filter((recipe) => recipe.tags.includes(tag)) : recipes;
    res.type('text').send(list.map((recipe) => recipe.title).join('\n'));
});

app.get('/recipes/:id', (req, res) => {
    const recipe = recipes.find((r) => r.id === Number(req.params.id));
    if (!recipe) {
        res.status(404).send('No such recipe');
        return;
    }
    res.send(recipe.title);
});

app.get('/api/recipes', (req, res) => {
    res.json(recipes);
});

app.get('/api/recipes/:id', (req, res) => {
    const recipe = recipes.find((r) => r.id === Number(req.params.id));
    if (!recipe) {
        res.status(404).json({ error: 'No such recipe' });
        return;
    }
    res.json(recipe);
});

app.get('/about', (req, res) => {
    res.send('Recipe Box collects family recipes.');
});

app.get('/menu', (req, res) => {
    res.redirect(301, '/recipes');
});

app.get('/menu/:id', (req, res) => {
    res.redirect(301, `/recipes/${req.params.id}`);
});

app.listen(3000, () => {
    console.log('Recipe Box is running on port 3000');
});