diff --git a/javascript/chronometer.js b/javascript/chronometer.js
index 7a1349680..c5bb8d737 100644
--- a/javascript/chronometer.js
+++ b/javascript/chronometer.js
@@ -1,34 +1,56 @@
 class Chronometer {
   constructor() {
     // ... your code goes here
+    this.currentTime = 0;
+    this.intervalId = null;
   }
 
   start(callback) {
     // ... your code goes here
+    this.intervalId = setInterval(() => {
+      this.currentTime++;
+      if (typeof callback === 'function') {
+        callback();
+      }
+    }, 1000);
   }
 
   getMinutes() {
     // ... your code goes here
+    return Math.floor(this.currentTime / 60);
   }
 
   getSeconds() {
     // ... your code goes here
+    return this.currentTime % 60;
   }
 
   computeTwoDigitNumber(value) {
     // ... your code goes here
+    return ('0' + value).slice(-2);
   }
 
   stop() {
     // ... your code goes here
+    if (this.intervalId !== null) {
+      clearInterval(this.intervalId);
+      this.intervalId = null;
+    }
   }
 
   reset() {
     // ... your code goes here
+    this.currentTime = 0;
   }
 
   split() {
     // ... your code goes here
+    const minutes = this.getMinutes();
+    const seconds = this.getSeconds();
+    const formattedMinutes = this.computeTwoDigitNumber(minutes);
+    const formattedSeconds = this.computeTwoDigitNumber(seconds);
+
+    return `${formattedMinutes}:${formattedSeconds}`;
   }
 }
 
diff --git a/javascript/index.js b/javascript/index.js
index fb3a43ab4..c0ff3afa8 100644
--- a/javascript/index.js
+++ b/javascript/index.js
@@ -15,14 +15,22 @@ const splitsElement = document.getElementById('splits');
 
 function printTime() {
   // ... your code goes here
+  printMinutes();
+  printSeconds();
 }
 
 function printMinutes() {
   // ... your code goes here
+  const minutes = chronometer.computeTwoDigitNumber(chronometer.getMinutes());
+  minDecElement.innerHTML = minutes[0];
+  minUniElement.innerHTML = minutes[1];
 }
 
 function printSeconds() {
   // ... your code goes here
+  const seconds = chronometer.computeTwoDigitNumber(chronometer.getSeconds());
+  secDecElement.innerHTML = seconds[0];
+  secUniElement.innerHTML = seconds[1];
 }
 
 // ==> BONUS
@@ -32,34 +40,69 @@ function printMilliseconds() {
 
 function printSplit() {
   // ... your code goes here
+  const splitTime = chronometer.split();
+  const listItem = document.createElement('li');
+  listItem.classList.add('list-item');
+  listItem.innerHTML = splitTime;
+  splitsElement.appendChild(listItem);
 }
 
 function clearSplits() {
   // ... your code goes here
+  splitsElement.innerHTML = '';
 }
 
 function setStopBtn() {
   // ... your code goes here
+  btnLeftElement.innerHTML = 'STOP';
+  btnLeftElement.classList.remove('start');
+  btnLeftElement.classList.add('stop');
 }
 
 function setSplitBtn() {
   // ... your code goes here
+  btnRightElement.innerHTML = 'SPLIT';
+  btnRightElement.classList.remove('reset');
+  btnRightElement.classList.add('split');
 }
 
 function setStartBtn() {
   // ... your code goes here
+  btnLeftElement.innerHTML = 'START';
+  btnLeftElement.classList.remove('stop');
+  btnLeftElement.classList.add('start');
 }
 
 function setResetBtn() {
   // ... your code goes here
+  btnRightElement.innerHTML = 'RESET';
+  btnRightElement.classList.remove('split');
+  btnRightElement.classList.add('reset');
 }
 
 // Start/Stop Button
 btnLeftElement.addEventListener('click', () => {
   // ... your code goes here
+  if (btnLeftElement.classList.contains('start')) {
+    setStopBtn();
+    setSplitBtn();
+    chronometer.start(printTime);
+  } else {
+    setStartBtn();
+    setResetBtn();
+    chronometer.stop();
+  }
 });
 
 // Reset/Split Button
 btnRightElement.addEventListener('click', () => {
   // ... your code goes here
+  if (btnRightElement.classList.contains('reset')) {
+    chronometer.reset();
+    printTime();
+    clearSplits();
+  } else {
+    printSplit();
+  }
+
 });