diff --git a/javascript/chronometer.js b/javascript/chronometer.js
index 7a1349680..435a4a451 100644
--- a/javascript/chronometer.js
+++ b/javascript/chronometer.js
@@ -1,34 +1,46 @@
 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 / 6000);
   }
 
   getSeconds() {
-    // ... your code goes here
+    return Math.floor((this.currentTime / 100) % 60);
+  }
+
+  getMilliseconds() {
+    return this.currentTime % 100;
   }
 
   computeTwoDigitNumber(value) {
-    // ... your code goes here
+    return value < 10 ? `0${value}` : `${value}`;
   }
 
   stop() {
-    // ... your code goes here
+    clearInterval(this.intervalId);
+    this.intervalId = null;
   }
 
   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..65fa72ce7 100644
--- a/javascript/index.js
+++ b/javascript/index.js
@@ -1,10 +1,8 @@
 const chronometer = new Chronometer();
 
-// get the buttons:
 const btnLeftElement = document.getElementById('btnLeft');
 const btnRightElement = document.getElementById('btnRight');
 
-// get the DOM elements that will serve us to display the time:
 const minDecElement = document.getElementById('minDec');
 const minUniElement = document.getElementById('minUni');
 const secDecElement = document.getElementById('secDec');
@@ -14,52 +12,82 @@ 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());
+  minDec.innerHTML = minutes[0];
+  minUni.innerHTML = minutes[1];
 }
 
 function printSeconds() {
-  // ... your code goes here
+  const seconds = chronometer.computeTwoDigitNumber(chronometer.getSeconds());
+  secDec.innerHTML = seconds[0];
+  secUni.innerHTML = seconds[1];
 }
 
 // ==> BONUS
 function printMilliseconds() {
-  // ... your code goes here
+  const milliseconds = chronometer.computeTwoDigitNumber(
+    chronometer.getMilliseconds()
+  );
+  milDecElement.innerHTML = milliseconds[0];
+  milUniElement.innerHTML = milliseconds[1];
 }
 
 function printSplit() {
-  // ... your code goes here
+  const li = document.createElement('li');
+  li.textContent = chronometer.split();
+  splitsElement.appendChild(li);
 }
 
 function clearSplits() {
-  // ... your code goes here
+  splitsElement.innerHTML = '';
 }
 
 function setStopBtn() {
-  // ... your code goes here
+  btnLeftElement.classList.add('stop');
+  btnLeftElement.textContent = 'STOP';
 }
 
 function setSplitBtn() {
-  // ... your code goes here
+  btnRightElement.classList.add('split');
+  btnRightElement.textContent = 'SPLIT';
 }
 
 function setStartBtn() {
-  // ... your code goes here
+  btnLeftElement.classList.remove('stop');
+  btnLeftElement.textContent = 'START';
 }
 
 function setResetBtn() {
-  // ... your code goes here
+  btnRightElement.classList.remove('split');
+  btnRightElement.textContent = 'RESET';
 }
 
 // Start/Stop Button
 btnLeftElement.addEventListener('click', () => {
-  // ... your code goes here
+  if (btnLeftElement.classList.contains('stop')) {
+    setStartBtn();
+    setResetBtn();
+    chronometer.stop();
+  } else {
+    setStopBtn();
+    setSplitBtn();
+    chronometer.start(printTime);
+  }
 });
 
 // Reset/Split Button
 btnRightElement.addEventListener('click', () => {
-  // ... your code goes here
+  if (btnRightElement.classList.contains('split')) {
+    printSplit();
+  } else {
+    chronometer.reset();
+    clearSplits();
+    printTime();
+  }
 });