public/web-development/presentation.git

			@@ -2125,6 +2125,485 @@
			</code>
			</pre>
			</section>
			<section>
			<h3>this</h3>
			<pre>
			<code class="js" data-trim data-line-numbers>
			class MyClass {
			constructor(a) {
			this.a = a;
			}

			getA() {
			return this.a;
			}
			}

			const x = new MyClass(5);
			const y = new MyClass(10);

			console.log(x.getA());
			console.log(y.getA());
			</code>
			</pre>
			<pre>
			<code class="bash" data-trim data-line-numbers>
			5
			10
			</code>
			</pre>
			</section>
			<section>
			<pre>
			<code class="js" data-trim data-line-numbers>
			global.a = 5;

			function foo() {
			this.a += 10;
			}

			foo();

			console.log(a);
			</code>
			</pre>
			<pre>
			<code class="bash" data-trim data-line-numbers>
			15
			</code>
			</pre>
			</section>
			<section>
			<pre>
			<code class="js" data-trim data-line-numbers>
			class MyClass {
			/* ... */
			setA() {
			function f() {
			this.a += 100;
			}
			f();
			}
			}

			const x = new MyClass(5);

			x.setA();

			console.log(x.getA());
			</code>
			</pre>
			<pre>
			<code class="bash" data-trim data-line-numbers>
			TypeError: Cannot read property 'a' of undefined
			</code>
			</pre>
			</section>
			<section>
			<pre>
			<code class="js" data-trim data-line-numbers>
			class MyClass {
			/* ... */
			setA() {
			const me = this;
			function f() {
			me.a += 100;
			}
			f();
			}
			}

			const x = new MyClass(5);

			x.setA();

			console.log(x.getA());
			</code>
			</pre>
			<pre>
			<code class="bash" data-trim data-line-numbers>
			105
			</code>
			</pre>
			</section>
			<section>
			<h3>Arrow-Funktionen</h3>
			<ul>
			<li>Kompakte Schreibweise einer normalen Funktion</li>
			<li>Bei Einzeilern ist das <code>return</code> nicht notwendig</li>
			<li>this-Pointer des aktuellen Kontextes wird beibehalten</li>
			</ul>
			<pre>
			<code class="js" data-trim data-line-numbers>
			// Einzeiler
			const f1 = _ => 1;
			const f2 = () => 1;
			const f3 = (x) => x * x;
			const f4 = (x, y) => x + y;

			// Mehrzeiler
			const f5 = (x, y) => {
			return x * y;
			};
			</code>
			</pre>
			</section>
			<section>
			<pre>
			<code class="js" data-trim data-line-numbers>
			class MyClass {
			/* ... */
			setA() {
			const f = () => {
			this.a += 100;
			}
			f();
			}
			}

			const x = new MyClass(5);

			x.setA();

			console.log(x.getA());
			</code>
			</pre>
			<pre>
			<code class="bash" data-trim data-line-numbers>
			105
			</code>
			</pre>
			</section>
			<section>
			<h3>Generator-Funktionen</h3>
			<pre>
			<code class="js" data-trim data-line-numbers>
			function* generator() {
			let i = 0;

			while(true) {
			yield i;
			i++;
			}
			}

			const g = generator();

			console.log(g.next().value);
			console.log(g.next().value);
			console.log(g.next().value);
			</code>
			</pre>
			<pre>
			<code class="bash" data-trim data-line-numbers>
			1
			2
			3
			</code>
			</pre>
			</section>
			<section>
			<h3>Generator-Funktionen</h3>
			<pre>
			<code class="js" data-trim data-line-numbers>
			function* generator() {
			yield 1;
			yield 2;
			yield 3;
			}

			const g = generator();

			for (const i of g) {
			console.log(i);
			}
			</code>
			</pre>
			<pre>
			<code class="bash" data-trim data-line-numbers>
			1
			2
			3
			</code>
			</pre>
			</section>
			<section>
			<h3>Nützliche Array-Funktionen</h3>
			</section>
			<section>
			Aufgabe: Schreibe ein Programm, das den Gesamtumsatz aus dem ersten Halbjahr berechnet
			<pre>
			<code class="js" data-trim data-line-numbers>
			const revenues = [
			{month: 0, revenue: 1000},
			{month: 1, revenue: 2000},
			{month: 2, revenue: 3000},
			{month: 3, revenue: 4000},
			{month: 4, revenue: 5000},
			{month: 5, revenue: 6000},
			{month: 6, revenue: 6000},
			{month: 7, revenue: 5000},
			{month: 8, revenue: 4000},
			{month: 9, revenue: 3000},
			{month: 10, revenue: 2000},
			{month: 11, revenue: 1000}
			];

			let totalRevenue = 0;

			/* ... */

			console.log(totalRevenue);
			</code>
			</pre>
			</section>
			<section>
			Lösung
			<pre>
			<code class="js" data-trim data-line-numbers>
			totalRevenue = revenues
			.filter((revenue) => revenue.month < 6)
			.map((revenue) => revenue.amount)
			.reduce((sum, amount) => sum + amount, 0);
			</code>
			</pre>
			<pre>
			<code class="bash" data-trim data-line-numbers>
			21000
			</code>
			</pre>
			</section>
			<section>
			<pre>
			<code class="js" data-trim data-line-numbers>
			const a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

			a.filter((e) => e > 2); // Filterung
			a.map((e) => e * 2); // Umformung
			a.reduce((p, e) => p + e, 0); // Zusammenrechnung / Reduzierung
			a.some((e) => e > 5); // true wenn min. ein Element die Bedingung erfüllt
			a.every((e) => e > 5); // true wenn alle Elemente die Bedingung erfüllen
			</code>
			</pre>
			</section>
			<section>
			<h3>Map</h3>
			<ul>
			<li>auch als "assoziatives Array" bezeichnet</li>
			<li>iterierbare Liste</li>
			<li>ideal zur Assoziation von z.B. Hashes zu Objekt-Instanzen o.ä.</li>
			<li>nutzbar ab es6 / es2015</li>
			<li>löst herkömmliche Objekte als Hash-Map ab</li>
			</ul>
			</section>
			<section>
			<pre>
			<code class="js" data-trim data-line-numbers>
			const m = new Map();

			m.set("a", 0);
			m.set("a", 1);
			m.set("b", 2);

			m.has("c"); // => false

			m.delete("b");

			console.log(m.get("a")); // => 1
			</code>
			</pre>
			</section>
			<section>
			<pre>
			<code class="js" data-trim data-line-numbers>
			m.forEach((k, v) => console.log(k, v)) // => "a" 1 ...

			for (const entry of m.entries()) {
			console.log(entry); // => ["a", 1] ...
			}

			for (const key of m.keys()) {
			console.log(key); // => "a" ...
			}

			for (const value of m.values()) {
			console.log(value); // => "1" ...
			}
			</code>
			</pre>
			</section>
			<section>
			<h3>Set</h3>
			<ul>
			<li>enthält nur einzigartige Werte</li>
			<li>iterierbare Liste</li>
			<li>ideale Struktur, wenn einzelne Werte einzigartig sein sollen</li>
			<li>nutzbar ab es6 / es2015</li>
			<li>löst individuelle Lösungen mittels Arrays und Array.prototype.indexOf o.ä. ab</li>
			</ul>
			</section>
			<section>
			<pre>
			<code class="js" data-trim data-line-numbers>
			const s = new Set();

			s.add("a");
			s.add("a");

			s.has("c"); // => false

			s.delete("a");

			console.log(s.size); // => 0
			</code>
			</pre>
			</section>
			<section>
			<pre>
			<code class="js" data-trim data-line-numbers>
			s.forEach((k, v) => console.log(k, v)) // => "a" "a" ...

			for (const entry of m.entries()) {
			console.log(entry); // => ["a", "a"] ...
			}

			for (const key of m.keys()) {
			console.log(key); // => "a"...
			}

			for (const value of s.values()) {
			console.log(value); // => "a" ...
			}
			</code>
			</pre>
			</section>
			<section>
			<h3>DOM-Events</h3>
			<ul>
			<li>funktionale Ausführung von Code</li>
			<li>Trigger können Klicks, Scrollen, Tastendrücke, Änderungen der Fenstergröße usw. sein</li>
			</ul>
			</section>
			<section>
			<img data-src="/assets/images/dom-events.svg">
			</section>
			<section>
			<pre>
			<code class="js" data-trim data-line-numbers>
			function doSomething(e) {
			console.log("capture");
			}

			function click(e) {
			console.log("bubble");
			}

			div.addEventListener("click", doSomething, true);

			button.addEventListener("click", click, false /* default */);
			</code>
			</pre>
			<pre>
			<code class="bash" data-trim data-line-numbers>
			capturing
			bubble
			</code>
			</pre>
			</section>
			<section>
			<p>Aufgabe: Erweitere das vorherige Beispiel so, dass das div-Element einen weiteren Click-Handler bekommt,
			der den Text "bubble2" anzeigt, nachdem "bubble" in der Konsole geloggt wurde.</p>

			<p>Erwartete Ausgabe:</p>
			<pre>
			<code class="bash" data-trim data-line-numbers>
			capturing
			bubble
			bubble2
			</code>
			</pre>
			</section>
			<section>
			<p>Lösung:</p>
			<pre>
			<code class="js" data-trim data-line-numbers>
			function doSomething(e) {
			console.log("capture");
			}

			// neu
			function doSomething2(e) {
			console.log("bubble2");
			}

			function click(e) {
			console.log("bubble");
			}

			div.addEventListener("click", doSomething, true);
			div.addEventListener("click", doSomething2, false); // neu

			button.addEventListener("click", click, false /* default */);
			</code>
			</pre>
			</section>
			<section>
			Die Bubble-Phase stoppen
			<pre>
			<code class="js" data-trim data-line-numbers>
			function click(e) {
			e.stopPropagation()
			}
			</code>
			</pre>
			</section>
			<section>
			<p>Aufgabe: Ändere das Ergebnis des vorherigen Beispiels, sodass die Bubble-Phase auf Ebene des button-Elements gestoppt wird. Was ändert sich in der Ausgabe?</p>
			</section>
			<section>
			<p>Lösung:</p>
			<pre>
			<code class="js" data-trim data-line-numbers>
			function doSomething(e) {
			console.log("capture");
			}

			function doSomething2(e) {
			console.log("bubble2");
			}

			function click(e) {
			e.stopPropagation();
			console.log("bubble");
			}

			div.addEventListener("click", doSomething, true);
			div.addEventListener("click", doSomething2, false);

			button.addEventListener("click", click, false /* default */);
			</code>
			</pre>
			</section>
			<section>
			Events programatisch triggern:
			<pre>
			<code class="js" data-trim data-line-numbers>
			button.dispatchEvent(new Event("click"));
			</code>
			</pre>
			</section>
			<section>
			Events sind synchron:
			<pre>
			<code class="js" data-trim data-line-numbers>
			doSomethingElse();

			button.dispatchEvent(new Event("click"));

			doAnotherThing(); // wird erst ausgeführt, wenn zuvor alle Event-Handler fertig sind
			</code>
			</pre>
			</section>
			</section>
			</div>
			</div>