solution

src/app.js

@@ -1 +1,36 @@
+/* eslint-disable no-console */
 'use strict';
+
+const readline = require('readline');
+const { generateRandomNumber } = require('./numberGenerator');
+const { calculateBullsAndCows } = require('./bullsAndCowsCalculator');
+
+const rl = readline.createInterface({
+  input: process.stdin,
+  output: process.stdout,
+});
+
+const secretNumber = generateRandomNumber();
+
+function playGame() {
+  rl.question('Enter your guess: ', (guessedNumber) => {
+    if (guessedNumber.length !== 4 || !/^\d{4}$/.test(guessedNumber)) {
+      playGame();
+
+      return;
+    }
+
+    const result = calculateBullsAndCows(secretNumber, guessedNumber);
+
+    if (result.bulls === 4) {
+      console.log('Congratulations you are win!!!!');
+      rl.close();
+    } else {
+      // eslint-disable-next-line no-console
+      console.log(`Bulls: ${result.bulls}, Cows: ${result.cows}`);
+      playGame();
+    }
+  });
+}
+
+playGame();

src/bullsAndCowsCalculator.js

@@ -0,0 +1,22 @@
+'use strict';
+
+function calculateBullsAndCows(secretNumber, guessedNumber) {
+  let bulls = 0;
+  let cows = 0;
+
+  for (let i = 0; i < 4; i++) {
+    if (guessedNumber[i] === secretNumber[i]) {
+      bulls++;
+    } else if (secretNumber.includes(guessedNumber[i])) {
+      cows++;
+    }
+  }
+
+  return {
+    bulls, cows,
+  };
+}
+
+module.exports = {
+  calculateBullsAndCows,
+};

src/numberGenerator.js

@@ -0,0 +1,20 @@
+'use strict';
+
+function generateRandomNumber() {
+  let digits = '0123456789';
+  let randomNum = '';
+
+  while (randomNum.length < 4) {
+    const randomDigitIndex = Math.floor(Math.random() * digits.length);
+
+    randomNum += digits[randomDigitIndex];
+
+    digits += digits.slice(randomDigitIndex, 1);
+  }
+
+  return randomNum;
+}
+
+module.exports = {
+  generateRandomNumber,
+};