diff --git a/javascript/chronometer.js b/javascript/chronometer.js
index 7a1349680..32a60b2bb 100644
--- a/javascript/chronometer.js
+++ b/javascript/chronometer.js
@@ -1,34 +1,45 @@
 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 (callback) callback();
+    }, 10);
   }
 
   getMinutes() {
-    // ... your code goes here
+    return Math.floor(this.currentTime / 60);
   }
 
   getSeconds() {
-    // ... your code goes here
+    return this.currentTime % 60;
+  }
+
+  getMilliseconds() {
+    return this.currentTime % 100;
   }
 
   computeTwoDigitNumber(value) {
-    // ... your code goes here
+    return value < 10 ? '0' + value : String(value);
   }
 
   stop() {
-    // ... your code goes here
+    clearInterval(this.intervalId);
   }
 
   reset() {
-    // ... your code goes here
+    this.currentTime = 0;
   }
 
   split() {
-    // ... your code goes here
+    const minutes = this.computeTwoDigitNumber(this.getMinutes());
+    const seconds = this.computeTwoDigitNumber(this.getSeconds());
+    const milliseconds = this.computeTwoDigitNumber(this.getMilliseconds());
+    return `${minutes}:${seconds}.${milliseconds}`;
   }
 }
 
diff --git a/javascript/index.js b/javascript/index.js
index fb3a43ab4..1a467fca2 100644
--- a/javascript/index.js
+++ b/javascript/index.js
@@ -14,52 +14,78 @@ const milUniElement = document.getElementById('milUni');
 const splitsElement = document.getElementById('splits');
 
 function printTime() {
-  // ... your code goes here
+  printMinutes();
+  printSeconds();
+  printMilliseconds();
 }
 
 function printMinutes() {
-  // ... your code goes here
+  const minutes = chronometer.computeTwoDigitNumber(chronometer.getMinutes());
+  minDecElement.innerText = minutes[0];
+  minUniElement.innerText = minutes[1];
 }
 
 function printSeconds() {
-  // ... your code goes here
+  const seconds = chronometer.computeTwoDigitNumber(chronometer.getSeconds());
+  secDecElement.innerText = seconds[0];
+  secUniElement.innerText = seconds[1];
 }
 
-// ==> BONUS
 function printMilliseconds() {
-  // ... your code goes here
+  const milliseconds = chronometer.computeTwoDigitNumber(chronometer.getMilliseconds());
+  milDecElement.innerText = milliseconds[0];
+  milUniElement.innerText = milliseconds[1];
 }
 
 function printSplit() {
-  // ... your code goes here
-}
-
-function clearSplits() {
-  // ... your code goes here
+  const li = document.createElement('li');
+  li.className = 'list-item';
+  li.innerText = chronometer.split();
+  splitsElement.appendChild(li);
 }
 
 function setStopBtn() {
-  // ... your code goes here
+  btnLeftElement.innerText = 'STOP';
+  btnLeftElement.className = 'btn stop';
 }
 
 function setSplitBtn() {
-  // ... your code goes here
+  btnRightElement.innerText = 'SPLIT';
+  btnRightElement.className = 'btn split';
 }
 
 function setStartBtn() {
-  // ... your code goes here
+  btnLeftElement.innerText = 'START';
+  btnLeftElement.className = 'btn start';
 }
 
 function setResetBtn() {
-  // ... your code goes here
+  btnRightElement.innerText = 'RESET';
+  btnRightElement.className = 'btn reset';
 }
 
 // Start/Stop Button
 btnLeftElement.addEventListener('click', () => {
-  // ... your code goes here
+  if (btnLeftElement.classList.contains('start')) {
+    // STOP/SPLIT
+    chronometer.start(printTime);
+    setStopBtn();
+    setSplitBtn();
+  } else {
+    // START/RESET
+    chronometer.stop();
+    setStartBtn();
+    setResetBtn();
+  }
 });
 
 // Reset/Split Button
 btnRightElement.addEventListener('click', () => {
-  // ... your code goes here
+  if (btnRightElement.classList.contains('reset')) {
+    chronometer.reset();
+    printTime();
+    clearSplits();
+  } else {
+    printSplit();
+  }
 });
diff --git a/tests/chronometer.spec.js b/tests/chronometer.spec.js
index 798db97a2..e9ff0f3f5 100755
--- a/tests/chronometer.spec.js
+++ b/tests/chronometer.spec.js
@@ -185,15 +185,15 @@ describe('Chronometer', () => {
 
     // If you decide to work on the bonus iteration,
     // comment the previous test and uncomment the following
-    // it('should return valid format with minutes, seconds and milliseconds', () => {
-    //   let min = chronometer.getMinutes();
-    //   let sec = chronometer.getSeconds();
-    //   let milli = chronometer.getMilliseconds();
-    //   if (min < 10) {
-    //     expect(chronometer.split()).toEqual(`0${min}:0${sec}:0${milli}`);
-    //   } else {
-    //     expect(chronometer.split()).toEqual(`${min}:${sec}:${milli}`);
-    //   }
-    // });
+    it('should return valid format with minutes, seconds and milliseconds', () => {
+      let min = chronometer.getMinutes();
+      let sec = chronometer.getSeconds();
+      let milli = chronometer.getMilliseconds();
+      if (min < 10) {
+        expect(chronometer.split()).toEqual(`0${min}:0${sec}:0${milli}`);
+      } else {
+        expect(chronometer.split()).toEqual(`${min}:${sec}:${milli}`);
+      }
+    });
   });
 });