reset button

app.js

@@ -24,15 +24,23 @@ const displayTime = () => {
 document.querySelector('.btn-primary').addEventListener('click', (event) => {
     document.querySelector('.btn-primary').disabled=true;
     document.querySelector('.btn-secondary').disabled=false;
+    document.querySelector('.btn-danger').disabled=true;
     windowInterval = window.setInterval(displayTime,1000)
 })
 
 document.querySelector('.btn-secondary').addEventListener('click', (event) => {
     document.querySelector('.btn-primary').disabled=false;
     document.querySelector('.btn-secondary').disabled=true;
+    document.querySelector('.btn-danger').disabled=false;
     window.clearInterval(windowInterval)
 })
 
+document.querySelector('.btn-danger').addEventListener('click', (event) => {
+    startTime = 0;
+    document.querySelector('h1').innerHTML = formatTime(startTime);
+    document.querySelector('.btn-danger').disabled=true;
+})
+
 // window.onbeforeunload = function(){
 //     return 'Good bye';
 // }

index.html

@@ -13,6 +13,7 @@
         <main class="container-fluid">
             <button type="button" class="btn btn-primary">Start</button>
             <button type="button" disabled class="btn btn-secondary">Stop</button>
+            <button type="button" disabled class="btn btn-danger">Reset</button>
             <h1></h1>
         </main>
         <script src="app.js" charset="utf-8"></script>