Summary - Express basics

Combine express, app.get and app.listen to write an API.

Summary - Express basics

In this group you learned the core tools of Express: creating an application with express(), defining GET routes with app.get, defining POST routes with app.post and starting the server with app.listen.

Now you will combine them into a small API. The API will return a JSON response to the /api path. This mini task shows how Express's core tools combine in a real API.

API design

The API skeleton: an application with express(), a route with app.get and a server with app.listen. The /api path gets a JSON response.

Flow: const app = express(); app.get("/api", (req, res) => res.json({ status: "ok" })); app.listen(3000, () => console.log("Server started"));. A /api request gets {"status":"ok"}. res.json sends an object as a JSON response; the content type is set automatically. Express lets you do this with far shorter code than the http module.

Exercise Write an Express API

Import express and create app. Define a route with app.get("/api", (req, res) => res.json({ status: "ok" })). The ready-made code below starts the server and sends a request to /api.

Show example solution

const express = require("express");
const app = express();
app.get("/api", (req, res) => res.json({ status: "ok" }));

const server = app.listen(3000, () => {
  const http = require("http");
  http.get("http://localhost:3000/api", (res) => {
    let body = "";
    res.on("data", (c) => body += c);
    res.on("end", () => { console.log("Reply: " + body); server.close(); });
  });
});

Test yourself

What pieces does the Express API combine?
```
app.get('/api', (req, res) => res.json(...))
```
- express(), app.get ve app.listen
- Only require
- Only console.log
- Only res.send
Show answer

express(), app.get ve app.listen — express() + app.get + app.listen combine.
Match each tool to its role

express()

Creates the application
app.get

Defines a route
res.json

Sends a JSON response
app.listen

Starts the server

Next lesson: What is middleware?

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