disable button while submitting

ui/static/ui/button.js

@@ -19,6 +19,7 @@ var button = document.getElementById("BUTTON");
 var count = document.getElementById("COUNT");
 
 button.addEventListener("click", event => {
+    button.disabled = true;
     fetch('/button', {
         method: 'POST',
         headers: {
@@ -31,6 +32,8 @@ button.addEventListener("click", event => {
         })
         .then((data) => {
             count.innerText = data.pressed;
+        }).finally(() => {
+            button.disabled = false;
         });
 });