diff --git a/javascript/chronometer.js b/javascript/chronometer.js
index 7a1349680..7f886ec1a 100644
--- a/javascript/chronometer.js
+++ b/javascript/chronometer.js
@@ -1,34 +1,55 @@
 class Chronometer {
   constructor() {
     // ... your code goes here
-  }
 
+    this.currentTime= 0; 
+    this.intervalId= null;
+
+  }
+  
   start(callback) {
-    // ... your code goes here
+    this.intervalId= setInterval(()=> {
+      this.currentTime= this.currentTime+1 ;
+    }, 1000);
+    callback(this.intervalId)
+  
   }
 
   getMinutes() {
     // ... your code goes here
+    const minutes= Math.floor (this.currentTime/60);
+    return minutes
   }
-
   getSeconds() {
     // ... your code goes here
+    const seconds= Math.floor(this.currentTime%60);
+    return seconds
   }
 
   computeTwoDigitNumber(value) {
+    let twoDigits = value.toString();
+      if (value.length < 2) {
+        numStr = '0' + numStr;
+      }
+      return twoDigits;
     // ... your code goes here
   }
 
   stop() {
     // ... your code goes here
+    clearInterval(this.intervalId); 
+    this.intervalId= null;
   }
 
   reset() {
     // ... your code goes here
+    this.currentTime=0
   }
 
   split() {
+    let split= (this.getMinutes()) + ":"+ (this.getSeconds())
     // ... your code goes here
+    return split
   }
 }
 
diff --git a/javascript/index.js b/javascript/index.js
index fb3a43ab4..4da91eb1f 100644
--- a/javascript/index.js
+++ b/javascript/index.js
@@ -18,15 +18,12 @@ function printTime() {
 }
 
 function printMinutes() {
+  minUniElement.innerText = chronometer.getMinutes() 
   // ... your code goes here
 }
 
 function printSeconds() {
-  // ... your code goes here
-}
-
-// ==> BONUS
-function printMilliseconds() {
+  secUniElement.innerText = chronometer.getSeconds()
   // ... your code goes here
 }
 
@@ -47,6 +44,7 @@ function setSplitBtn() {
 }
 
 function setStartBtn() {
+  chronometer.start()
   // ... your code goes here
 }
 
@@ -56,6 +54,18 @@ function setResetBtn() {
 
 // Start/Stop Button
 btnLeftElement.addEventListener('click', () => {
+  const leftButton = document.getElementById("btnLeft");
+  const rightButton = document.getElementById("btnRight");
+  if (leftButton.innerHTML === "START") {
+    btnLeftElement.addEventListener('click', chronometer.start());
+    leftButton.innerHTML = "STOP";
+    rightButton.innerHTML = "SLICE";
+  } else {
+    btnLeftElement.addEventListener('click', setStopBtn);
+    leftButton.innerHTML = "START";
+    rightButton.innerHTML = "RESET";
+  }
+
   // ... your code goes here
 });
 
@@ -63,3 +73,5 @@ btnLeftElement.addEventListener('click', () => {
 btnRightElement.addEventListener('click', () => {
   // ... your code goes here
 });
+
+