express()

Learn to create an app with express().

Creating an app with express()

The express() call creates an Express application (app). This application is the main object that manages routes and the server. Signature: const app = express();.

On the app object you define routes (app.get, app.post) and start the server (app.listen). Example: const express = require("express"); const app = express();. After this you access all Express features through app. express() returns a new, independent application object each time it is called, so in a project it is usually called once.

The app object

The app object is the heart of an Express application. On it you define routes, add middleware and start the server. All Express workflow revolves around app.

Example: const app = express(); creates the application. Then app.get("/", handler) adds a route. app.listen(3000) starts the server. app is an object; methods are called on it with a dot. The name is usually app but you can name it anything. What matters is that all route and server calls are on the same app object.

Exercise Create an Express application

Import the express module. Create app with the express() call. Print "App ready" with console.log.

Show example solution

const express = require("express");
const app = express();
console.log("App ready");

Test yourself

Complete the app creation line

const app = ____();

Show answer

const app = express();

What does express() return?
```
const app = express()
```
- An Express application (app)
- Bir dize
- A number
- Bir http sunucusu
Show answer

An Express application (app) — express() returns an app object.
Match each method to its role

express()

Creates the application
app.get

Defines a GET route
app.post

Defines a POST route
app.listen

Starts the server

Next lesson: app.get

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