From 8c6e3cd02ee8931ffffe9f760fb5013112141276 Mon Sep 17 00:00:00 2001
From: Sascha Schulz <sschulz@dh-software.de>
Date: Do, 25 Mai 2023 11:04:31 +0200
Subject: [PATCH] Merge branch 'draft'
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</pre>
</section>
</section>
+ <section>
+ <section>
+ <h2>JavaScript</h2>
+ </section>
+ <section>
+ <style>
+ table.my-table td:not(:first-child) {
+ text-align: center;
+ }
+
+ table.my-table td:not(:last-child), table.my-table th:not(:last-child) {
+ border-right: 1px solid white;
+ }
+
+ table.my-table td {
+ vertical-align: middle;
+ }
+ </style>
+ <table class="my-table">
+ <tr>
+ <th></th>
+ <th>c / c++</th>
+ <th>Java</th>
+ <th>C#</th>
+ <th>JS</th>
+ </tr>
+ <tr>
+ <td>Formale Spezifikation</td>
+ <td colspan="4" class="fragment">ja</td>
+ </tr>
+ <tr>
+ <td>Ãœbersetzung</td>
+ <td class="fragment">Nativ kompiliert</td>
+ <td class="fragment" colspan="2">Bytecode</td>
+ <td class="fragment">Interpretiert / kompiliert (JIT)</td>
+ </tr>
+ <tr>
+ <td>Typisierung</td>
+ <td colspan="3" class="fragment">statisch</td>
+ <td class="fragment">dynamisch</td>
+ </tr>
+ <tr>
+ <td>Speicher-Management</td>
+ <td class="fragment">Manuell</td>
+ <td class="fragment" colspan="3">Garbage Collector</td>
+ </tr>
+ </table>
+ </section>
+ <section>
+ <h3>Begrifflichkeiten</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ function add(x, y) {
+ return x + y;
+ }
+
+ const a = 5;
+ const b = add(a, 6);
+ const c = [];
+ </code>
+ </pre>
+ <div><span class="fragment">Operator, </span><span class="fragment">Aufruf (Call), </span><span class="fragment">Ausdruck (Expression), </span><span class="fragment">Parameter, </span><span class="fragment">Argument, </span><span class="fragment">Literal, </span></div><div><span class="fragment">Zuweisung (Assignment), </span><span class="fragment">Linke Hand (Left hand), Rechte Hand (Right hand)</span></div>
+ </section>
+ <section>
+ <h3>Vorbereiten der Beispiele (bei Bedarf)</h3>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ # im Ordner 'examples/'
+ . hooks/post-checkout
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Ausführung</h3>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ # node [Script-Datei], z.B.
+ node index.js
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Ausgaben</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ console.log("Hello World!");
+ </code>
+ </pre>
+ </section>
+
+ <section>
+ <h3>Variablen</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ // < es6
+ var x = 1;
+
+ // >= es6
+ let y = 2;
+ const z = 3;
+ </code>
+ </pre>
+ </section>
+ <section>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ var yes = false;
+
+ if (yes) {
+ var a = 1;
+ }
+
+ console.log(a);
+ </code>
+ </pre>
+ <pre class="fragment">
+ <code class="bash" data-trim data-line-numbers>
+ undefined
+ </code>
+ </pre>
+ </section>
+ <section>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ var yes = false;
+
+ if (yes) {
+ let a = 1;
+ }
+
+ console.log(a);
+ </code>
+ </pre>
+ <pre class="fragment">
+ <code class="bash" data-trim data-line-numbers>
+ ReferenceError: a is not defined
+ </code>
+ </pre>
+ </section>
+ <section>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ function foo() {
+ var yes = false;
+
+ if (yes) {
+ var a = 1;
+ }
+ }
+
+ foo();
+
+ console.log(a);
+ </code>
+ </pre>
+ <pre class="fragment">
+ <code class="bash" data-trim data-line-numbers>
+ ReferenceError: a is not defined
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3><code>var</code></h3>
+ <ul>
+ <li>hat <code>function</code>-Scope</li>
+ <li>wird durch <span class="italic">hoisting</span> ("hochziehen") aus dem Block heraus an den Start der Funktion gezogen</li>
+ </ul>
+ </section>
+ <section>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ var yes = false;
+ var a;
+
+ if (yes) {
+ a = 1;
+ }
+
+ console.log(a);
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3><code>let</code>, <code>const</code></h3>
+ <ul>
+ <li>haben intuitiven Block-Scope (wie viele andere Programmiersprachen auch)</li>
+ <li>daher nur an Ort und Stelle gültig in der angegebenen Reihenfolge</li>
+ </ul>
+ </section>
+ <section>
+ <h3>Datentypen</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ let x = 5; // Number (Integer)
+ let f = 1.25; // Number (Float)
+ let b = true; // Boolean
+ let s = "hallo"; // String
+ let a = []; // Array
+ let o = {}; // Objekt
+ let nan = NaN; // Not a Number
+ let n = null; // Null
+ let u = undefined; // Undefiniert
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Alternation</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ if (x == 1) {
+ // Code
+ }
+ else if (x == 2) {
+ // alternativer Code
+ }
+ else {
+ // Fallback
+ }
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Schleifen</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ for (let i = 0; i < 5; i++) {
+ // Code
+ }
+ </code>
+ </pre>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ const a = [1, 2, 3];
+
+ for (const element of a) {
+ // Code
+ }
+ </code>
+ </pre>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ while (i == 1) {
+ // Code
+ }
+ </code>
+ </pre>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ do {
+ // Code
+ } while (i == 1)
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Arrays</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ let a = [1, 2, 3];
+
+ a.push(4);
+ a.push(5);
+
+ a.pop();
+
+ console.log(a);
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ [1, 2, 3, 4]
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Objekte</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ let o = {x: 1, y: 2};
+
+ console.log(o.z);
+
+ console.log(o);
+
+ o.z = 3;
+
+ console.log(o);
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ undefined
+ { x: 1, y: 2 }
+ { x: 1, y: 2, z: 3 }
+ </code>
+ </pre>
+ </section>
+ <section>
+ <div>Objekte funktionieren intern wie Hash-Maps</div>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ let o = {};
+
+ o.a = 1;
+ o["a"] = 1; // alternativ
+
+ o["$ !"] = 2; // so sind auch komplexe Schlüssel möglich
+
+ // o."$ !" = 2; => Syntaxfehler
+ // o.$ ! = 2; => Syntaxfehler
+
+ o[true] = 3;
+
+ console.log(Object.keys(o));
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ [ 'a', '$ !', 'true' ]
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Funktionen</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ function foo() {
+ console.log("foo");
+ }
+
+ function bar(a) {
+ return a;
+ }
+
+ foo();
+
+ const a = bar(1);
+
+ console.log(a);
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ foo
+ 1
+ </code>
+ </pre>
+ </section>
+ <section>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ let sum = function(a, b) {
+ return a + b;
+ }
+
+ let subtract = function() {
+ console.log(arguments);
+
+ return arguments[0] - arguments[1];
+ }
+
+ console.log(sum(1, 2));
+ console.log(subtract(1, 2));
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ 3
+ [Arguments] { '0': 1, '1': 2 }
+ -1
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Funktionen als Konstruktor</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ function Rectangle(a, b) {
+ this.a = a;
+ this.b = b;
+ }
+
+ const r = new Rectangle(2, 3);
+
+ console.log(r.a);
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ 2
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Objektorientierung</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ function Rectangle(a, b) {
+ this.a = a;
+ this.b = b;
+ }
+
+ // jede Funktion besitzt einen Prototypen
+ Rectangle.prototype.getArea = function() {
+ return this.a * this.b;
+ }
+
+ const r1 = new Rectangle(2, 3);
+ const r2 = new Rectangle(4, 5);
+
+ console.log(r1.getArea());
+ console.log(r2.getArea());
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ 6
+ 20
+ </code>
+ </pre>
+ </section>
+ <section>
+ <img data-src="/assets/images/constructor-and-its-prototype.svg">
+ </section>
+ <section>
+ <div>Dynamische Änderung des Prototypen</div>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ function Rectangle(a, b) {
+ this.a = a;
+ this.b = b;
+ }
+
+ const r = new Rectangle(2, 3);
+
+ console.log(r.getArea);
+
+ Rectangle.prototype.getArea = function() {
+ return this.a * this.b;
+ }
+
+ console.log(r.getArea);
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ undefined
+ [Function (anonymous)]
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Aufgabe</h3>
+ Bringe dem Array eine Methode bei, welche die Summe aller enthaltenen Zahlen zurückgibt
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ const a = [1, 2, 3];
+
+ console.log(a.sum());
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ 6
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Lösung</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ Array.prototype.sum = function() {
+ let sum = 0;
+
+ for (let number of this) {
+ sum += number;
+ }
+
+ return sum;
+ }
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Vererbung</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers="1-13|15-18|20-29">
+ // Oberklasse
+ function Shape() {
+ }
+
+ Shape.prototype.getType = function() {
+ return "Shape";
+ }
+
+ // Unterklasse
+ function Rectangle(a, b) {
+ this.a = a;
+ this.b = b;
+ }
+
+ // Prototype der Oberklasse in die Unterklasse kopieren
+ Rectangle.prototype = Object.create(Shape.prototype);
+ // Konstruktor der Oberklasse am Prototypen durch den eigenen ersetzen
+ Rectangle.prototype.constructor = Rectangle;
+
+ const r = new Rectangle(2, 3);
+
+ console.log(r.getType());
+
+ // .getType() selber implementieren
+ Rectangle.prototype.getType = function() {
+ return "Rectangle";
+ }
+
+ console.log(r.getType());
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ Shape
+ Rectangle
+ </code>
+ </pre>
+ </section>
+ <section>
+ <img data-src="/assets/images/inheritance-es5.svg">
+ </section>
+ <section>
+ <div>
+ <img width="800" height="500" data-src="/assets/images/mdn-prototype.jpg">
+ </div>
+ <p>
+ <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/push" style="font-size: 16px">https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/push</a>
+ </p>
+ </section>
+ <section>
+ <h3>Objektorientierung in es6</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ class Rectangle {
+ constructor(a, b) {
+ this.a = a;
+ this.b = b;
+ }
+
+ getArea() {
+ return this.a * this.b;
+ }
+ }
+
+ const r = new Rectangle(2, 3);
+
+ console.log(r.getArea());
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ 6
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Vererbung in es6</h3>
+ <pre>
+ <code class="js" data-trim data-line-numbers="1-6|8-16|18-27">
+ // Oberklasse
+ class Shape {
+ getType() {
+ return "Shape";
+ }
+ }
+
+ // Unterklasse erbt von Oberklasse
+ class Rectangle extends Shape {
+ constructor(a, b) {
+ super();
+
+ this.a = a;
+ this.b = b;
+ }
+ }
+
+ const r = new Rectangle(2, 3);
+
+ console.log(r.getType());
+
+ // Implementierung per Prototype weiterhin möglich, falls man so will
+ Rectangle.prototype.getType = function() {
+ return "Rectangle";
+ }
+
+ console.log(r.getType());
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ Shape
+ Rectangle
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Asynchronität</h3>
+ <p>Asynchron: Es wird nicht auf die Beendigung des Befehls gewartet, sondern mit dem Programm fortgefahren. Die Vollendung des asynchronen Befehls tritt <i style="font-style: italic">irgendwann</i> in der Zukunft ein.</p>
+ </section>
+ <section>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ setTimeout(callback, time); // Ausführung nach [time] Millisekunden
+ setInterval(callback, interval); // Ausführung alle [interval] Millisekunden
+ </code>
+ </pre>
+ </section>
+ <section>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ setTimeout(function() {
+ // Code, der nach 2 Sekunden ausgeführt wird
+ console.log("zweiter");
+ }, 2000);
+
+ console.log("erster");
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ erster
+ zweiter
+ </code>
+ </pre>
+ </section>
+ <section>
+ <p>Aufgabe: Schreibe ein Programm, das zwei weitere beliebige Texte mit jeweils 2 Sekunden Verzögerung von einander ausgibt, d.h.</p>
+ <p>"erster" -> 2s -> "zweiter" -> 2s -> "Text A" -> 2s -> "Text B"</p>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ setTimeout(function() {
+ console.log("zweiter");
+
+ // weiterer Code
+ }, 2000);
+
+ console.log("erster");
+ </code>
+ </pre>
+ </section>
+ <section>
+ Lösung: Callback-Hell oder Pyramide des Todes
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ setTimeout(function() {
+ console.log("zweiter");
+
+ setTimeout(function() {
+ console.log("Text A");
+
+ setTimeout(function() {
+ console.log("Text B");
+
+
+ }, 2000);
+ }, 2000);
+ }, 2000);
+
+ console.log("erster");
+ </code>
+ </pre>
+ </section>
+ <section>
+ Hilfsmittel: Promises
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ new Promise(function (resolve, reject) {
+ // ich bin fertig
+ resolve();
+
+ // es ist ein Fehler aufgetreten
+ reject();
+ });
+ </code>
+ </pre>
+ </section>
+ <section>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ const p = new Promise(function (resolve, reject) {...});
+ const p2 = new Promise(function (resolve, reject) {...});
+ const p3 = new Promise(function (resolve, reject) {...});
+ const p4 = new Promise(function (resolve, reject) {...});
+
+ p
+ .then(function() { return p2; })
+ .then(function() { return p3; })
+ .then(function() { return p4; });
+ </code>
+ </pre>
+ </section>
+ <section>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ console.log("erster");
+
+ delay(2000)
+ .then(function () {
+ console.log("zweiter");
+
+ return delay(2000);
+ })
+ .then(function() {
+ console.log("Text A");
+
+ return delay(2000);
+ })
+ .then(function() {
+ console.log("Text B");
+ })
+ </code>
+ </pre>
+ </section>
+ <section>
+ Aufgabe: Implementiere die Funktion "delay"
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ const delay = function() {
+ // implementieren
+ }
+
+ console.log("erster");
+
+ delay(2000)
+ .then(function () {
+ console.log("zweiter");
+
+ return delay(2000);
+ })
+ .then(function() {
+ console.log("Text A");
+
+ return delay(2000);
+ })
+ .then(function() {
+ console.log("Text B");
+ })
+ </code>
+ </pre>
+ </section>
+ <section>
+ Lösung:
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ const delay = function(ms) {
+ return new Promise(function(resolve, reject) {
+ setTimeout(function() {
+ resolve();
+ }, ms);
+ });
+ }
+
+ console.log("erster");
+
+ delay(2000)
+ .then(function () {
+ console.log("zweiter");
+
+ return delay(2000);
+ })
+ .then(function() {
+ console.log("Text A");
+
+ return delay(2000);
+ })
+ .then(function() {
+ console.log("Text B");
+ })
+ </code>
+ </pre>
+ </section>
+ <section>
+ Rückgabewerte mit Promises
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ const p = new Promise(function(resolve, reject) {
+ resolve("ok");
+ });
+
+ p.then(function(value) {
+ console.log(value);
+ });
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ ok
+ </code>
+ </pre>
+ </section>
+ <section>
+ Fehlerbehandlung mit Promises
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ const p = new Promise(function(resolve, reject) {
+ reject(new Error("Fehler"));
+ });
+
+ p
+ .then(function() {
+ console.log("Ich werde nicht aufgerufen")
+ })
+ .catch(function(e) {
+ console.log(e.message);
+ });
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ Fehler
+ </code>
+ </pre>
+ </section>
+ <section>
+ Datei lesen mit NodeJS
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ const fs = require("fs");
+
+ fs.readFile("./hello.txt", {encoding: "utf8"}, function(data) {
+ console.log(data);
+ });
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ Hello World!
+
+ </code>
+ </pre>
+ </section>
+ <section>
+ Aufgabe: "Promisifiziere" analog zu "delay" in der letzten Aufgabe den Aufruf von fs.readFile()
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ const fs = require("fs");
+
+ function readFile() {
+ // implementieren
+ }
+
+ readFile.then(function(content) {
+ console.log(content);
+ });
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ Hello World!
+ </code>
+ </pre>
+ </section>
+ <section>
+ Aufgabe: Nutze die vorherige Lösung nun für eine Promise-Kette, sodass die Inhalte der zwei Dateien "hello.txt" und "hallo.txt" nacheinander ausgegeben werden:
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ Hello World!
+
+ Hallo Welt!
+
+ </code>
+ </pre>
+ </section>
+ <section>
+ <h3>Async - Await</h3>
+ <ul>
+ <li>Syntaktischer Zucker für Promises</li>
+ <li>Nutzung von <code>await</code> nur im Kontext einer <code>async</code>-Funktion möglich</li>
+ </ul>
+ <pre>
+ <code class="js" data-trim data-line-numbers>
+ async function wrapper() {
+ const p = new Promise(function(resolve, reject) {
+ resolve("Hello from Promise!");
+ });
+
+ const result = await p;
+
+ console.log(result);
+ }
+
+ wrapper();
+ </code>
+ </pre>
+ <pre>
+ <code class="bash" data-trim data-line-numbers>
+ Hello from Promise!
+ </code>
+ </pre>
+ </section>
+ <section>
+ Aufgabe: Schreibe die Lösung der vorherigen Aufgabe nach Async - Await um
+ </section>
+ </section>
</div>
</div>
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