diff --git a/03_js-dom/unterricht/tag20/03_chat-lernheft/assets/css/styles.css b/03_js-dom/unterricht/tag20/03_chat-lernheft/assets/css/styles.css
new file mode 100644
index 0000000..8122b3d
--- /dev/null
+++ b/03_js-dom/unterricht/tag20/03_chat-lernheft/assets/css/styles.css
@@ -0,0 +1,368 @@
+/* -------------------------------------------- Haupt CSS fuer alle Seiten -------------------------------------------- */
+
+/* ---------------- CSS-Reset ------------------- */
+html,
+body,
+a,
+div,
+h1,
+h2,
+h3,
+h4,
+h5,
+h6,
+span,
+p,
+img,
+strong,
+ul,
+li,
+table,
+th,
+td,
+tr {
+  margin: 0px;
+  padding: 0px;
+  border: 0px none;
+  font-weight: normal;
+  font-style: inherit;
+  font-family: inherit;
+  font-variant: inherit;
+  text-decoration: none;
+  table-layout: inherit;
+}
+
+/* ---------------- Body / HTML ------------------- */
+
+html {
+  font-size: 100%;
+  background-color: #fffef7;
+}
+
+body {
+  font-family: Helvetica, Arial, sans-serif;
+  font-size: 1.2em;
+  font-weight: normal;
+  color: black;
+  margin: 0rem auto 2rem auto;
+}
+
+/* ---------------- layout ------------------- */
+
+header {
+  background: url('../img/js_header.png') left top no-repeat transparent;
+  background-size: cover;
+  height: 250px;
+  min-width: 850px;
+}
+
+header:after {
+  content: ' ';
+  display: block;
+  height: 250px;
+  background: rgba(255, 254, 247, 0);
+  background: -moz-linear-gradient(
+    top,
+    rgba(255, 254, 247, 0) 0%,
+    rgba(255, 254, 247, 0.55) 22%,
+    rgba(255, 254, 247, 0.7) 42%,
+    rgba(255, 254, 247, 0.71) 43%,
+    rgba(255, 254, 247, 0.78) 61%,
+    rgba(255, 254, 247, 0.92) 75%,
+    rgba(255, 254, 247, 1) 87%,
+    rgba(255, 254, 247, 1) 100%
+  );
+  background: -webkit-gradient(
+    left top,
+    left bottom,
+    color-stop(0%, rgba(255, 254, 247, 0)),
+    color-stop(22%, rgba(255, 254, 247, 0.55)),
+    color-stop(42%, rgba(255, 254, 247, 0.7)),
+    color-stop(43%, rgba(255, 254, 247, 0.71)),
+    color-stop(61%, rgba(255, 254, 247, 0.78)),
+    color-stop(75%, rgba(255, 254, 247, 0.92)),
+    color-stop(87%, rgba(255, 254, 247, 1)),
+    color-stop(100%, rgba(255, 254, 247, 1))
+  );
+  background: -webkit-linear-gradient(
+    top,
+    rgba(255, 254, 247, 0) 0%,
+    rgba(255, 254, 247, 0.55) 22%,
+    rgba(255, 254, 247, 0.7) 42%,
+    rgba(255, 254, 247, 0.71) 43%,
+    rgba(255, 254, 247, 0.78) 61%,
+    rgba(255, 254, 247, 0.92) 75%,
+    rgba(255, 254, 247, 1) 87%,
+    rgba(255, 254, 247, 1) 100%
+  );
+  background: -o-linear-gradient(
+    top,
+    rgba(255, 254, 247, 0) 0%,
+    rgba(255, 254, 247, 0.55) 22%,
+    rgba(255, 254, 247, 0.7) 42%,
+    rgba(255, 254, 247, 0.71) 43%,
+    rgba(255, 254, 247, 0.78) 61%,
+    rgba(255, 254, 247, 0.92) 75%,
+    rgba(255, 254, 247, 1) 87%,
+    rgba(255, 254, 247, 1) 100%
+  );
+  background: -ms-linear-gradient(
+    top,
+    rgba(255, 254, 247, 0) 0%,
+    rgba(255, 254, 247, 0.55) 22%,
+    rgba(255, 254, 247, 0.7) 42%,
+    rgba(255, 254, 247, 0.71) 43%,
+    rgba(255, 254, 247, 0.78) 61%,
+    rgba(255, 254, 247, 0.92) 75%,
+    rgba(255, 254, 247, 1) 87%,
+    rgba(255, 254, 247, 1) 100%
+  );
+  background: linear-gradient(
+    to bottom,
+    rgba(255, 254, 247, 0) 0%,
+    rgba(255, 254, 247, 0.55) 22%,
+    rgba(255, 254, 247, 0.7) 42%,
+    rgba(255, 254, 247, 0.71) 43%,
+    rgba(255, 254, 247, 0.78) 61%,
+    rgba(255, 254, 247, 0.92) 75%,
+    rgba(255, 254, 247, 1) 87%,
+    rgba(255, 254, 247, 1) 100%
+  );
+  filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#fffef7', endColorstr='#fffef7', GradientType=0 );
+  filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#fffef7', endColorstr='#fffef7', GradientType=0 );
+}
+
+main,
+footer {
+  width: 70%;
+  margin: 3rem auto;
+  min-width: 850px;
+  padding: 0 20px;
+  box-sizing: border-box;
+}
+
+/* ---------------- Content ------------------- */
+
+h1 {
+  color: #93412b;
+  font-size: 3em;
+  margin-bottom: 20px;
+  font-weight: bold;
+}
+
+h2 {
+  color: #93412b;
+  font-size: 2.5em;
+  margin-bottom: 15px;
+}
+
+h3 {
+  color: #93412b;
+  font-size: 2em;
+  margin-bottom: 10px;
+}
+
+p {
+  line-height: 15px;
+  margin-bottom: 15px;
+  line-height: 1.7em;
+}
+
+.cited {
+  font-style: italic;
+  font-size: 0.8em;
+}
+
+.u {
+  text-decoration: underline;
+}
+.b {
+  font-weight: bold;
+}
+.i {
+  font-style: italic;
+}
+.align_right {
+  text-align: right;
+}
+.align_left {
+  text-align: left;
+  margin-right: 10px;
+}
+.align_center {
+  text-align: center;
+}
+.float_left {
+  float: left;
+}
+.float_right {
+  float: right;
+}
+.clear_both {
+  clear: both;
+}
+strong {
+  font-weight: bold;
+}
+.special {
+  color: #b7595b;
+  font-weight: bold;
+}
+.keyword {
+  color: #db6f50;
+  font-weight: bold;
+  font-style: italic;
+}
+.gray {
+  color: gray;
+}
+
+/* Links */
+main a:link,
+main a:visited {
+  color: #eb690b;
+  font-weight: bold;
+}
+
+main a:focus,
+main a:hover,
+main a:active {
+  color: #eb690b;
+}
+
+ul {
+  list-style-position: outside;
+  margin-bottom: 20px;
+  padding-left: 22px;
+}
+
+ol {
+  margin-bottom: 20px;
+  padding-left: 30px;
+}
+
+li {
+  line-height: 1.4em;
+}
+
+/* ------- Article ------- */
+
+h1 {
+  color: #93412b;
+  font-size: 2.7em;
+  margin-bottom: 20px;
+}
+
+#buy_form input[type='button'] {
+  display: inline-block;
+  padding: 1px 20px 3px 20px;
+  background-color: #93412b;
+  color: white;
+  border: 1px solid white;
+  font-size: 1em;
+  height: 32px;
+}
+
+#buy_form input[type='button']:hover {
+  background-color: white;
+  color: #93412b;
+  border: 1px solid #93412b;
+}
+
+#buy_form select {
+  display: inline-block;
+  font-size: 1em;
+  background-color: white;
+  color: #93412b;
+  border: 1px solid #93412b;
+  height: 32px;
+}
+
+/* ------- Chat ------- */
+
+#chat {
+  width: 100%;
+  background-color: white;
+  border: 1px solid #9c352f;
+  height: 20rem;
+  position: relative;
+}
+
+#chat_window {
+  background-color: white;
+  width: 85%;
+  float: left;
+  height: 95%;
+}
+
+#chat_history {
+  position: absolute;
+  bottom: 8%;
+  max-height: 92%;
+  padding: 0px 0px 5px 7px;
+}
+
+#chat_history p {
+  font-size: 0.6em;
+  margin: 0;
+}
+
+#chat_text {
+  height: 8%;
+  position: absolute;
+  bottom: 0;
+  width: 85%;
+}
+
+#chat_text input {
+  width: 98%;
+  display: block;
+  margin: auto;
+}
+
+#chat_members {
+  list-style-type: none;
+  height: 100%;
+  width: 15%;
+  margin-left: 85%;
+  border-left: 1px solid #9c352f;
+  text-align: right;
+  box-sizing: border-box;
+  min-width: 100px;
+  font-size: 0.8em;
+  padding-top: 5px;
+}
+
+#chat_members li {
+  line-height: 1.2em;
+  padding: 5px 10px 2px 15px;
+}
+
+#chat_members .highlighted {
+  background-color: #c14d45;
+  color: white;
+}
+.chat_member {
+  font-weight: bold;
+}
+.chat_member1 {
+  color: #3626c8;
+}
+.chat_member2 {
+  color: #e38d0b;
+}
+
+#member_search {
+  position: absolute;
+  right: 0;
+  bottom: 0;
+  width: 15%;
+  height: 8%;
+}
+
+#member_search input {
+  width: 88%;
+  display: block;
+  margin: auto;
+  text-align: right;
+}
diff --git a/03_js-dom/unterricht/tag20/03_chat-lernheft/assets/img/favicon.ico b/03_js-dom/unterricht/tag20/03_chat-lernheft/assets/img/favicon.ico
new file mode 100644
index 0000000..bd2cd28
Binary files /dev/null and b/03_js-dom/unterricht/tag20/03_chat-lernheft/assets/img/favicon.ico differ
diff --git a/03_js-dom/unterricht/tag20/03_chat-lernheft/assets/img/js_header.png b/03_js-dom/unterricht/tag20/03_chat-lernheft/assets/img/js_header.png
new file mode 100644
index 0000000..4d14ceb
Binary files /dev/null and b/03_js-dom/unterricht/tag20/03_chat-lernheft/assets/img/js_header.png differ
diff --git a/03_js-dom/unterricht/tag20/03_chat-lernheft/assets/js/main.js b/03_js-dom/unterricht/tag20/03_chat-lernheft/assets/js/main.js
new file mode 100644
index 0000000..4871b12
--- /dev/null
+++ b/03_js-dom/unterricht/tag20/03_chat-lernheft/assets/js/main.js
@@ -0,0 +1,19 @@
+'use strict';
+
+{
+  const highlightChatMembersBy = (partOfMemberName) => {
+    chatMembers()
+      .filter((member) => doesMemberMatch(partOfMemberName, member))
+      .forEach(highlight);
+  };
+
+  const doesMemberMatch = (partOfMemberName, member) =>
+    member.innerHTML.toLowerCase().includes(partOfMemberName.toLowerCase());
+
+  const chatMembers = () => $$('#chat_members li');
+  const highlight = (el) => el.classList.add('highlighted');
+
+  const $$ = (qs) => Array.from(document.querySelectorAll(qs));
+
+  highlightChatMembersBy('ert');
+}
diff --git a/03_js-dom/unterricht/tag20/03_chat-lernheft/index.html b/03_js-dom/unterricht/tag20/03_chat-lernheft/index.html
new file mode 100644
index 0000000..4cda3e6
--- /dev/null
+++ b/03_js-dom/unterricht/tag20/03_chat-lernheft/index.html
@@ -0,0 +1,53 @@
+<!doctype html>
+<html lang="de">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>classList - DOMTokenList</title>
+    <!-- <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.8/dist/css/bootstrap.min.css" rel="stylesheet" /> -->
+    <link rel="stylesheet" href="assets/css/styles.css" />
+    <link rel="shortcut icon" href="assets/img/favicon.ico" type="image/x-icon" />
+    <script src="assets/js/main.js" defer></script>
+  </head>
+  <body>
+    <header></header>
+    <main>
+      <div class="container py-5">
+        <h1>classList - <a href="https://developer.mozilla.org/de/docs/Web/API/DOMTokenList">DOMTokenList</a></h1>
+        <hr />
+        <h2>The Chat</h2>
+        <div id="chat">
+          <div id="chat_window">
+            <div id="chat_history">
+              <p>
+                <span class="chat_member chat_member1">Ladislaus:</span>
+                Anybody there?
+              </p>
+              <p>
+                <span class="chat_member chat_member2">Friedlinde</span>
+                Yes, me!
+              </p>
+            </div>
+
+            <div id="chat_text">
+              <input type="text" placeholder="...new message..." />
+            </div>
+          </div>
+
+          <ul id="chat_members">
+            <li class="admin">Heribert</li>
+            <li>Friedlinde</li>
+            <li>Tusnelda</li>
+            <li>Berthold</li>
+            <li>Oswine</li>
+            <li>Ladislaus</li>
+          </ul>
+
+          <div id="member_search">
+            <input type="text" placeholder="...Find a member..." />
+          </div>
+        </div>
+      </div>
+    </main>
+  </body>
+</html>
diff --git a/03_js-dom/unterricht/tag20/04_chat-refactored/assets/css/styles.css b/03_js-dom/unterricht/tag20/04_chat-refactored/assets/css/styles.css
new file mode 100644
index 0000000..8122b3d
--- /dev/null
+++ b/03_js-dom/unterricht/tag20/04_chat-refactored/assets/css/styles.css
@@ -0,0 +1,368 @@
+/* -------------------------------------------- Haupt CSS fuer alle Seiten -------------------------------------------- */
+
+/* ---------------- CSS-Reset ------------------- */
+html,
+body,
+a,
+div,
+h1,
+h2,
+h3,
+h4,
+h5,
+h6,
+span,
+p,
+img,
+strong,
+ul,
+li,
+table,
+th,
+td,
+tr {
+  margin: 0px;
+  padding: 0px;
+  border: 0px none;
+  font-weight: normal;
+  font-style: inherit;
+  font-family: inherit;
+  font-variant: inherit;
+  text-decoration: none;
+  table-layout: inherit;
+}
+
+/* ---------------- Body / HTML ------------------- */
+
+html {
+  font-size: 100%;
+  background-color: #fffef7;
+}
+
+body {
+  font-family: Helvetica, Arial, sans-serif;
+  font-size: 1.2em;
+  font-weight: normal;
+  color: black;
+  margin: 0rem auto 2rem auto;
+}
+
+/* ---------------- layout ------------------- */
+
+header {
+  background: url('../img/js_header.png') left top no-repeat transparent;
+  background-size: cover;
+  height: 250px;
+  min-width: 850px;
+}
+
+header:after {
+  content: ' ';
+  display: block;
+  height: 250px;
+  background: rgba(255, 254, 247, 0);
+  background: -moz-linear-gradient(
+    top,
+    rgba(255, 254, 247, 0) 0%,
+    rgba(255, 254, 247, 0.55) 22%,
+    rgba(255, 254, 247, 0.7) 42%,
+    rgba(255, 254, 247, 0.71) 43%,
+    rgba(255, 254, 247, 0.78) 61%,
+    rgba(255, 254, 247, 0.92) 75%,
+    rgba(255, 254, 247, 1) 87%,
+    rgba(255, 254, 247, 1) 100%
+  );
+  background: -webkit-gradient(
+    left top,
+    left bottom,
+    color-stop(0%, rgba(255, 254, 247, 0)),
+    color-stop(22%, rgba(255, 254, 247, 0.55)),
+    color-stop(42%, rgba(255, 254, 247, 0.7)),
+    color-stop(43%, rgba(255, 254, 247, 0.71)),
+    color-stop(61%, rgba(255, 254, 247, 0.78)),
+    color-stop(75%, rgba(255, 254, 247, 0.92)),
+    color-stop(87%, rgba(255, 254, 247, 1)),
+    color-stop(100%, rgba(255, 254, 247, 1))
+  );
+  background: -webkit-linear-gradient(
+    top,
+    rgba(255, 254, 247, 0) 0%,
+    rgba(255, 254, 247, 0.55) 22%,
+    rgba(255, 254, 247, 0.7) 42%,
+    rgba(255, 254, 247, 0.71) 43%,
+    rgba(255, 254, 247, 0.78) 61%,
+    rgba(255, 254, 247, 0.92) 75%,
+    rgba(255, 254, 247, 1) 87%,
+    rgba(255, 254, 247, 1) 100%
+  );
+  background: -o-linear-gradient(
+    top,
+    rgba(255, 254, 247, 0) 0%,
+    rgba(255, 254, 247, 0.55) 22%,
+    rgba(255, 254, 247, 0.7) 42%,
+    rgba(255, 254, 247, 0.71) 43%,
+    rgba(255, 254, 247, 0.78) 61%,
+    rgba(255, 254, 247, 0.92) 75%,
+    rgba(255, 254, 247, 1) 87%,
+    rgba(255, 254, 247, 1) 100%
+  );
+  background: -ms-linear-gradient(
+    top,
+    rgba(255, 254, 247, 0) 0%,
+    rgba(255, 254, 247, 0.55) 22%,
+    rgba(255, 254, 247, 0.7) 42%,
+    rgba(255, 254, 247, 0.71) 43%,
+    rgba(255, 254, 247, 0.78) 61%,
+    rgba(255, 254, 247, 0.92) 75%,
+    rgba(255, 254, 247, 1) 87%,
+    rgba(255, 254, 247, 1) 100%
+  );
+  background: linear-gradient(
+    to bottom,
+    rgba(255, 254, 247, 0) 0%,
+    rgba(255, 254, 247, 0.55) 22%,
+    rgba(255, 254, 247, 0.7) 42%,
+    rgba(255, 254, 247, 0.71) 43%,
+    rgba(255, 254, 247, 0.78) 61%,
+    rgba(255, 254, 247, 0.92) 75%,
+    rgba(255, 254, 247, 1) 87%,
+    rgba(255, 254, 247, 1) 100%
+  );
+  filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#fffef7', endColorstr='#fffef7', GradientType=0 );
+  filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#fffef7', endColorstr='#fffef7', GradientType=0 );
+}
+
+main,
+footer {
+  width: 70%;
+  margin: 3rem auto;
+  min-width: 850px;
+  padding: 0 20px;
+  box-sizing: border-box;
+}
+
+/* ---------------- Content ------------------- */
+
+h1 {
+  color: #93412b;
+  font-size: 3em;
+  margin-bottom: 20px;
+  font-weight: bold;
+}
+
+h2 {
+  color: #93412b;
+  font-size: 2.5em;
+  margin-bottom: 15px;
+}
+
+h3 {
+  color: #93412b;
+  font-size: 2em;
+  margin-bottom: 10px;
+}
+
+p {
+  line-height: 15px;
+  margin-bottom: 15px;
+  line-height: 1.7em;
+}
+
+.cited {
+  font-style: italic;
+  font-size: 0.8em;
+}
+
+.u {
+  text-decoration: underline;
+}
+.b {
+  font-weight: bold;
+}
+.i {
+  font-style: italic;
+}
+.align_right {
+  text-align: right;
+}
+.align_left {
+  text-align: left;
+  margin-right: 10px;
+}
+.align_center {
+  text-align: center;
+}
+.float_left {
+  float: left;
+}
+.float_right {
+  float: right;
+}
+.clear_both {
+  clear: both;
+}
+strong {
+  font-weight: bold;
+}
+.special {
+  color: #b7595b;
+  font-weight: bold;
+}
+.keyword {
+  color: #db6f50;
+  font-weight: bold;
+  font-style: italic;
+}
+.gray {
+  color: gray;
+}
+
+/* Links */
+main a:link,
+main a:visited {
+  color: #eb690b;
+  font-weight: bold;
+}
+
+main a:focus,
+main a:hover,
+main a:active {
+  color: #eb690b;
+}
+
+ul {
+  list-style-position: outside;
+  margin-bottom: 20px;
+  padding-left: 22px;
+}
+
+ol {
+  margin-bottom: 20px;
+  padding-left: 30px;
+}
+
+li {
+  line-height: 1.4em;
+}
+
+/* ------- Article ------- */
+
+h1 {
+  color: #93412b;
+  font-size: 2.7em;
+  margin-bottom: 20px;
+}
+
+#buy_form input[type='button'] {
+  display: inline-block;
+  padding: 1px 20px 3px 20px;
+  background-color: #93412b;
+  color: white;
+  border: 1px solid white;
+  font-size: 1em;
+  height: 32px;
+}
+
+#buy_form input[type='button']:hover {
+  background-color: white;
+  color: #93412b;
+  border: 1px solid #93412b;
+}
+
+#buy_form select {
+  display: inline-block;
+  font-size: 1em;
+  background-color: white;
+  color: #93412b;
+  border: 1px solid #93412b;
+  height: 32px;
+}
+
+/* ------- Chat ------- */
+
+#chat {
+  width: 100%;
+  background-color: white;
+  border: 1px solid #9c352f;
+  height: 20rem;
+  position: relative;
+}
+
+#chat_window {
+  background-color: white;
+  width: 85%;
+  float: left;
+  height: 95%;
+}
+
+#chat_history {
+  position: absolute;
+  bottom: 8%;
+  max-height: 92%;
+  padding: 0px 0px 5px 7px;
+}
+
+#chat_history p {
+  font-size: 0.6em;
+  margin: 0;
+}
+
+#chat_text {
+  height: 8%;
+  position: absolute;
+  bottom: 0;
+  width: 85%;
+}
+
+#chat_text input {
+  width: 98%;
+  display: block;
+  margin: auto;
+}
+
+#chat_members {
+  list-style-type: none;
+  height: 100%;
+  width: 15%;
+  margin-left: 85%;
+  border-left: 1px solid #9c352f;
+  text-align: right;
+  box-sizing: border-box;
+  min-width: 100px;
+  font-size: 0.8em;
+  padding-top: 5px;
+}
+
+#chat_members li {
+  line-height: 1.2em;
+  padding: 5px 10px 2px 15px;
+}
+
+#chat_members .highlighted {
+  background-color: #c14d45;
+  color: white;
+}
+.chat_member {
+  font-weight: bold;
+}
+.chat_member1 {
+  color: #3626c8;
+}
+.chat_member2 {
+  color: #e38d0b;
+}
+
+#member_search {
+  position: absolute;
+  right: 0;
+  bottom: 0;
+  width: 15%;
+  height: 8%;
+}
+
+#member_search input {
+  width: 88%;
+  display: block;
+  margin: auto;
+  text-align: right;
+}
diff --git a/03_js-dom/unterricht/tag20/04_chat-refactored/assets/img/favicon.ico b/03_js-dom/unterricht/tag20/04_chat-refactored/assets/img/favicon.ico
new file mode 100644
index 0000000..bd2cd28
Binary files /dev/null and b/03_js-dom/unterricht/tag20/04_chat-refactored/assets/img/favicon.ico differ
diff --git a/03_js-dom/unterricht/tag20/04_chat-refactored/assets/img/js_header.png b/03_js-dom/unterricht/tag20/04_chat-refactored/assets/img/js_header.png
new file mode 100644
index 0000000..4d14ceb
Binary files /dev/null and b/03_js-dom/unterricht/tag20/04_chat-refactored/assets/img/js_header.png differ
diff --git a/03_js-dom/unterricht/tag20/04_chat-refactored/assets/js/main.js b/03_js-dom/unterricht/tag20/04_chat-refactored/assets/js/main.js
new file mode 100644
index 0000000..b64299f
--- /dev/null
+++ b/03_js-dom/unterricht/tag20/04_chat-refactored/assets/js/main.js
@@ -0,0 +1,45 @@
+'use strict';
+
+// IIFE
+(() => {
+  // === DOM & VARS =======
+  const module = document.querySelector('#chat') || console.warn('Element not found');
+  const DOM = {
+    module,
+    listItems: Array.from(module.querySelectorAll('#chat_members li')),
+  };
+
+  console.log(DOM);
+  // === INIT =============
+  const init = () => {
+    // Funktionsaufruf zu beginn der Anwendung
+    highlightListItemsBy('ert');
+  };
+
+  // === EVENTHANDLER =====
+
+  // === XHR/FETCH ========
+
+  // === FUNCTIONS ========
+  const highlightListItemsBy = (searchValue = '') => {
+    DOM.listItems.forEach((el) => {
+      const text = el.textContent.trim().toLowerCase();
+      if (text.includes(searchValue.trim().toLowerCase())) {
+        // el.classList.add('highlighted');
+        addClass(el, 'highlighted');
+      }
+    });
+  };
+
+  // helpers
+  const addClass = (el, className) => {
+    if (Array.isArray(className)) {
+      el.classList.add(...className);
+    } else {
+      el.classList.add(className);
+    }
+    return el;
+  };
+
+  init();
+})();
diff --git a/03_js-dom/unterricht/tag20/04_chat-refactored/index.html b/03_js-dom/unterricht/tag20/04_chat-refactored/index.html
new file mode 100644
index 0000000..4cda3e6
--- /dev/null
+++ b/03_js-dom/unterricht/tag20/04_chat-refactored/index.html
@@ -0,0 +1,53 @@
+<!doctype html>
+<html lang="de">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>classList - DOMTokenList</title>
+    <!-- <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.8/dist/css/bootstrap.min.css" rel="stylesheet" /> -->
+    <link rel="stylesheet" href="assets/css/styles.css" />
+    <link rel="shortcut icon" href="assets/img/favicon.ico" type="image/x-icon" />
+    <script src="assets/js/main.js" defer></script>
+  </head>
+  <body>
+    <header></header>
+    <main>
+      <div class="container py-5">
+        <h1>classList - <a href="https://developer.mozilla.org/de/docs/Web/API/DOMTokenList">DOMTokenList</a></h1>
+        <hr />
+        <h2>The Chat</h2>
+        <div id="chat">
+          <div id="chat_window">
+            <div id="chat_history">
+              <p>
+                <span class="chat_member chat_member1">Ladislaus:</span>
+                Anybody there?
+              </p>
+              <p>
+                <span class="chat_member chat_member2">Friedlinde</span>
+                Yes, me!
+              </p>
+            </div>
+
+            <div id="chat_text">
+              <input type="text" placeholder="...new message..." />
+            </div>
+          </div>
+
+          <ul id="chat_members">
+            <li class="admin">Heribert</li>
+            <li>Friedlinde</li>
+            <li>Tusnelda</li>
+            <li>Berthold</li>
+            <li>Oswine</li>
+            <li>Ladislaus</li>
+          </ul>
+
+          <div id="member_search">
+            <input type="text" placeholder="...Find a member..." />
+          </div>
+        </div>
+      </div>
+    </main>
+  </body>
+</html>