diff --git a/javascript/chronometer.js b/javascript/chronometer.js
index 7a1349680..bbf94f228 100644
--- a/javascript/chronometer.js
+++ b/javascript/chronometer.js
@@ -1,34 +1,47 @@
 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(); // cada 10 ms se ejecuta el callback (la función que le pasemos)
+      }
+    }, 10); // Cada 10 ms incrementa el cronómetro (el update)
   }
 
   getMinutes() {
-    // ... your code goes here
+    return Math.floor(this.currentTime / 6000); // 6000 ms = 1 minuto
   }
 
   getSeconds() {
-    // ... your code goes here
+    return Math.floor((this.currentTime / 100) % 60); // 100 ms = 1 segundo
   }
 
-  computeTwoDigitNumber(value) {
-    // ... your code goes here
+  getMilliseconds() {
+    return this.currentTime % 100; // El resto son los ms
   }
 
-  stop() {
-    // ... your code goes here
+  computeTwoDigitNumber(value) {
+    return value.toString().padStart(2, '0'); // Asegura que siempre tenga 2 dígitos (1 = 01, ...)
   }
 
   reset() {
-    // ... your code goes here
+    this.currentTime = 0; // Reinicia el cronómetro a 0
+  }
+
+  stop() {
+    clearInterval(this.intervalId);
   }
 
   split() {
-    // ... your code goes here
+    return `${this.computeTwoDigitNumber(this.getMinutes())}
+    :${this.computeTwoDigitNumber(this.getSeconds())}
+    :${this.computeTwoDigitNumber(this.getMilliseconds())}`;
+    // Es extraña la línea pero devolvemos un string con el formato MM:SS:MS, siempre en el formate de 2 dígitos
   }
 }
 
diff --git a/javascript/index.js b/javascript/index.js
index fb3a43ab4..30262a463 100644
--- a/javascript/index.js
+++ b/javascript/index.js
@@ -14,52 +14,86 @@ const milUniElement = document.getElementById('milUni');
 const splitsElement = document.getElementById('splits');
 
 function printTime() {
-  // ... your code goes here
+  printMinutes();
+  printSeconds();
+  printMilliseconds(); // Bonus
 }
 
 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
+  const li = document.createElement('li');
+  li.className = 'list-item';
+  li.innerText = chronometer.split();
+  splitsElement.appendChild(li);
 }
 
 function clearSplits() {
-  // ... your code goes here
+  splitsElement.innerText = ''; // Limpia el contenido de la lista de elementos
 }
 
 function setStopBtn() {
-  // ... your code goes here
+  btnLeftElement.className = 'btn stop';
+  btnLeftElement.innerText = 'STOP';
 }
 
 function setSplitBtn() {
-  // ... your code goes here
+  btnRightElement.className = 'btn split';
+  btnRightElement.innerText = 'SPLIT';
 }
 
 function setStartBtn() {
-  // ... your code goes here
+  btnLeftElement.className = 'btn start';
+  btnLeftElement.innerText = 'START';
 }
 
 function setResetBtn() {
-  // ... your code goes here
+  btnRightElement.className = 'btn reset';
+  btnRightElement.innerText = 'RESET';
 }
 
 // Start/Stop Button
 btnLeftElement.addEventListener('click', () => {
-  // ... your code goes here
+  if (btnLeftElement.classList.contains('start')) {
+    chronometer.start(printTime);
+    setStopBtn();
+    setSplitBtn();
+  } else {
+    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();
+  }
 });