clarify attribute change example

Sascha Schulz

2024-02-05 904d9655997b1cb46bb8044843465c8045092af8

 index.html

@@ -3554,10 +3554,12 @@
               </section>
               <section>
                  <pre>
                     <code class="js" data-trim data-line-numbers="1-15|17">
                     <code class="js" data-trim data-line-numbers="1-16|19">
                        <script type="text/template">
                           class HelloWorldComponent extends HTMLElement {
                              connectedCallback() {
                              constructor() {
                                 super();
									
                                 const shadowRoot = this.attachShadow({mode: "open"});
                              
                                 shadowRoot.innerHTML = `
@@ -3581,14 +3583,44 @@
                  <iframe data-src="/assets/html/hello-world.html"></iframe>
               </section>
               <section>
                  <h4>Light DOM vs Shadow DOM</h4>
                  <img data-src="/assets/images/web-components-shadow-root.png" width="500px">
               </section>
               <section>
                  <h4>Suche von Elementen im Light- und Shadow DOM</h4>
                  <pre>
                     <code class="js" data-trim data-line-numbers>
                        <script type="text/template">
                           // Light DOM
                           const span = document.querySelector("span"); // Hi!
                           const divs = document.querySelectorAll("div");
									
                           console.log(divs.length); // => 1
									
                           // Shadow DOM
                           const helloWorld = document.querySelector("hello-world");
									
                           helloWorld.shadowRoot.querySelector("div"); // Hello World!
                        </script>
                     </code>
                  </pre>
               </section>
               <section>
                  <h3>Auf Attribute reagieren</h3>
                  <pre>
                     <code class=html data-trim data-line-numbers>
                        <script type="text/template">
                           <hello-world my-attribute="a"></hello-world>
                        </script>
                     </code>
                  </pre>
                  <pre>
                     <code class="js" data-trim data-line-numbers="2|8-10">
                        <script type="text/template">
                           class HelloWorldComponent extends HTMLElement {
                              static observedAttributes = ["my-attribute"];
                           
                              connectedCallback() {
                              constructor() {
                                 // ...
                              }
                           
@@ -3605,6 +3637,48 @@
                  <p>Lasse die eigene Komponente "hello-sayer" auf eine Änderung des "name"-Attributs reagieren, indem der dort eingetragene Name in der Komponente angezeigt wird (Beispiel: name="Joe" => Hello Joe!)</p>
                  <p>(/examples/templates/web-components/hello-sayer.html)</p>
               </section>
               <section>
                  <h3>Musterlösung</h3>
                  <pre>
                     <code class="js" data-trim data-line-numbers>
                        <script type="text/template">
                           class HelloSayerComponent extends HTMLElement {
                              static observedAttributes = ["name"];
									
                              constructor() {
                                 super();
									
                                 this.root = this.attachShadow({mode: "open"});
									
                                 this.root.innerHTML = `
                                    <style>
                                       div {
                                          background-color: coral;
                                          color: white;
                                       }
                                    </style>
                                    <div>Hello!</div>
                                 `;
                              }
									
                              attributeChangedCallback(name, oldValue, newValue) {
                                 this.root.querySelector("div").innerHTML = `Hello ${newValue}!`;
                              }
                           }
									
                           window.customElements.define("hello-sayer", HelloSayerComponent);
									
                           const names = ["Joe", "Allie"];
                           let counter = 0;
									
                           setInterval(() => document.querySelector("hello-sayer").setAttribute("name", names[counter++ % 2]), 2000);
                        </script>
                     </code>
                  </pre>
               </section>
               <section>
                  <iframe data-src="/assets/html/hello-sayer.html"></iframe>
               </section>
            </section>
         </div>
      </div>