working version

static/js/main.js

@@ -0,0 +1,34 @@
+(($) => {
+    var ws = new WebSocket("ws://localhost:8000/ws");
+    const input = $("#message");
+    const messages = $('#messages');
+    var lastMessage;
+
+    $('#button').on('click', () => {
+        const message = input.val();
+
+        if (message) {
+            ws.send(message);
+            lastMessage = $('<div class="message received"><p>Loading...</p></div>')
+            messages.append(`<div class="message sent"><p>${message}</p></div>`)
+            messages.append(lastMessage);
+
+            input.val("");
+        }
+    });
+
+    ws.onmessage = (event) => {
+        if (lastMessage.text() === "Loading...") {
+            lastMessage.empty();
+        }
+
+        var content = document.createTextNode(event.data);
+
+        if (content.textContent === "<<END>>") {
+            lastMessage.html(marked.parse(lastMessage.text()));
+        }
+        else {
+            lastMessage.append(content);
+        }
+    };
+})(jQuery);