diff --git a/javascript/chronometer.js b/javascript/chronometer.js
index 7a1349680..e071cb7dc 100644
--- a/javascript/chronometer.js
+++ b/javascript/chronometer.js
@@ -1,34 +1,61 @@
 class Chronometer {
   constructor() {
-    // ... your code goes here
+    this.currentTime = 0;
+    this.currentMilliseconds = 0;
+    this.intervalId = null;
+    this.millisecondsintervalId = null;
   }
 
   start(callback) {
-    // ... your code goes here
+    this.intervalId = setInterval(() => {
+      this.currentTime++;
+      if (callback) {
+        callback();
+      }
+    }, 1000);
+
+    this.millisecondIntervalId = setInterval(() => {
+      this.currentMilliseconds += 10;
+      if (this.currentMilliseconds >= 1000) {
+        this.currentMilliseconds = 0;
+      }
+      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 Math.floor(this.currentMilliseconds / 10);
   }
 
   computeTwoDigitNumber(value) {
-    // ... your code goes here
+    return value < 10 ? "0" + value : value.toString();
   }
 
   stop() {
-    // ... your code goes here
+    clearInterval(this.intervalId);
+    clearInterval(this.millisecondIntervalId);
+    this.intervalId = null;
+    this.millisecondIntervalId = null;
   }
 
   reset() {
-    // ... your code goes here
+    this.currentTime = 0;
+    this.currentMilliseconds = 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}`;
   }
 }
 
@@ -36,4 +63,4 @@ class Chronometer {
 /* Environment setup. Do not modify the below code. */
 if (typeof module !== 'undefined') {
   module.exports = Chronometer;
-}
+}
\ No newline at end of file
diff --git a/javascript/index.js b/javascript/index.js
index fb3a43ab4..f027860b2 100644
--- a/javascript/index.js
+++ b/javascript/index.js
@@ -14,52 +14,87 @@ 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.getMinutes();
+  const formattedMinutes = chronometer.computeTwoDigitNumber(minutes);
+
+  minDecElement.innerText = formattedMinutes[0];
+  minUniElement.innerText = formattedMinutes[1];
 }
 
 function printSeconds() {
-  // ... your code goes here
+  const seconds = chronometer.getSeconds();
+  const formattedSeconds = chronometer.computeTwoDigitNumber(seconds);
+
+  secDecElement.innerText = formattedSeconds[0];
+  secUniElement.innerText = formattedSeconds[1];
 }
 
 // ==> BONUS
 function printMilliseconds() {
-  // ... your code goes here
+  const milliseconds = chronometer.getMilliseconds();
+  const formattedMilliseconds = chronometer.computeTwoDigitNumber(milliseconds);
+  milDecElement.innerText = formattedMilliseconds[0];
+  milUniElement.innerText = formattedMilliseconds[1];
 }
 
 function printSplit() {
-  // ... your code goes here
+  const li = document.createElement('li');
+  li.innerText = chronometer.split();
+  splitsElement.appendChild(li);}
+
+function clearSplits() {
+  splitsElement.innerHTML = '';
 }
 
 function clearSplits() {
-  // ... your code goes here
+  splitsElement.innerHTML = '';
 }
 
 function setStopBtn() {
-  // ... your code goes here
+  btnLeftElement.className = "btn stop";
+  btnLeftElement.textContent = "STOP";
 }
 
 function setSplitBtn() {
-  // ... your code goes here
+  btnRightElement.className = "btn split";
+  btnRightElement.textContent = "SPLIT";
 }
 
 function setStartBtn() {
-  // ... your code goes here
+  btnLeftElement.className = "btn start";
+  btnLeftElement.textContent = "START";
 }
 
 function setResetBtn() {
-  // ... your code goes here
+  btnRightElement.className = "btn reset";
+  btnRightElement.textContent = "RESET";
 }
 
 // Start/Stop Button
 btnLeftElement.addEventListener('click', () => {
-  // ... your code goes here
+  if (btnLeftElement.classList.contains('start')) {
+    chronometer.start(printTime);
+    setStopBtn();
+    setSplitBtn();
+  } 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 if (btnRightElement.classList.contains('split')) {
+    printSplit();
+}});