Query Strings

Part of the Express Basics section of Coddy's Node.js journey. Lesson 5 of 20.

A list page often needs options, like which recipes to show, and a new route for each option would be too many.

app.get('/books', (req, res) => {
    const { author } = req.query;
    res.send(author ? 'Books by ' + author : 'All books');
});

The query string is the part of the URL after ?, and Express puts it in req.query. GET /books?author=Austen gives req.query.author === 'Austen'. With no ? it is undefined. Several options join with &: /books?author=Austen&year=1813.

A route parameter is part of the path and names one thing. A query option filters or sorts a list, and can be left out.

Challenge

Easy

GET /recipes?tag=vegan lists only the titles of recipes with that tag, one per line.
Without tag, it lists every title.

Send GET /recipes?tag=vegan, GET /recipes?tag=dessert and GET /recipes.

Try it yourself

import express from 'express';
import { recipes } from './data.js';

const app = express();

app.get('/', (req, res) => {
    res.send('Welcome to Recipe Box');
});

// type('text') sends plain text, so each title shows on its own line.
app.get('/recipes', (req, res) => {
    res.type('text').send(recipes.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('/about', (req, res) => {
    res.send('Recipe Box collects family recipes.');
});

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