Merge branch 'draft'

Sascha Schulz

2023-05-25 8c6e3cd02ee8931ffffe9f760fb5013112141276

 index.html

@@ -1642,6 +1642,159 @@
                     </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>