uni/slides/dhbw/03_nodejs_basics.md

marp, theme, paginate, backgroundColor, header, footer

marp	theme	paginate	backgroundColor	header	footer
true	gaia	true		Web Engineering – DHBW Stuttgart	Michael Czechowski – SoSe 2025

<style> :root { --color-foreground: #1a1a2e; --color-highlight: #005f8a; --color-dimmed: #4a6a7a; } section.invert { --color-foreground: #fff; } section { font-size: 1.7rem; } h1 { color: #005f8a; } section.invert h1 { color: #fff; } pre { background: #0f1e2e; color: #00b4d8; border-radius: 8px; border-left: 3px solid #005f8a; } pre code { background: transparent; color: inherit; } code { background: #1a3a4a; color: #00b4d8; padding: 0.15em 0.4em; border-radius: 4px; } a { color: var(--color-highlight); } </style>

Node.js – Scripting, Running and Building

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Node.js – Was ist das?

• JavaScript Runtime (V8 Engine)
• Server-side JavaScript
• npm Package Manager
• Ideal für: APIs, CLI Tools, Automation

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node --check und node -e

# Syntax check only
node --check script.js

# One-liner
node -e "console.log('Hallo Welt')"

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node -e Beispiele

# String
node -e "console.log('Hello ' + process.argv[2])" Welt

# File reading
node -e "console.log(require('fs').readFileSync('data.json'))"

# JSON parsen
node -e "console.log(JSON.parse(process.argv[1]))" '{"a":1}'

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require() – Module laden

// Eigene Datei
const utils = require('./utils');

// npm Modul
const express = require('express');

// Built-in
const fs = require('fs');
const path = require('path');

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__dirname und __filename

// Aktuelles Verzeichnis (Node.js)
console.log(__dirname);   // /home/user/project/src
console.log(__filename);  // /home/user/project/src/app.js

// Pfad joinen
const configPath = path.join(__dirname, '..', 'config.json');

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HTTP Server mit Node.js (Built-in)

const http = require('http');

const server = http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'text/html' });
  res.end('<h1>Hallo Welt!</h1>');
});

server.listen(3000, () => {
  console.log('Server läuft auf Port 3000');
});

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fs – Dateien lesen/schreiben

const fs = require('fs');

// Async
fs.readFile('data.json', 'utf8', (err, data) => {
  if (err) throw err;
  console.log(JSON.parse(data));
});

// Sync
const content = fs.readFileSync('data.json', 'utf8');

// Write
fs.writeFile('output.txt', 'Hallo Welt', (err) => {
  if (err) throw err;
});

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package.json – Das Herzstück

{
  "name": "mein-projekt",
  "version": "1.0.0",
  "main": "index.js",
  "scripts": {
    "start": "node index.js",
    "dev": "node --watch index.js",
    "test": "node --test"
  },
  "dependencies": {
    "express": "^4.18.0"
  },
  "devDependencies": {
    "nodemon": "^3.0.0"
  }
}

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npm Scripts

# npm run <script>
npm run start
npm run dev

# Mit Argumenten
npm run build -- --production

# Lifecycle scripts
npm install  → postinstall
npm start    → start (direkt)

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Node.js Module – exports

// utils.js
module.exports = {
  add: (a, b) => a + b,
  greet: (name) => `Hallo ${name}!`
};

// Oder einzelne Exporte
module.exports.add = (a, b) => a + b;

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Fragen?

1. Wie startest du einen Node.js Server auf Port 8080?
2. Was macht node --check?
3. Wozu dient package.json?