diff --git a/finance-tracker/.gitignore b/finance-tracker/.gitignore
new file mode 100644
index 0000000..b512c09
--- /dev/null
+++ b/finance-tracker/.gitignore
@@ -0,0 +1 @@
+node_modules
\ No newline at end of file
diff --git a/finance-tracker/.prettierrc b/finance-tracker/.prettierrc
new file mode 100644
index 0000000..5fb6e1a
--- /dev/null
+++ b/finance-tracker/.prettierrc
@@ -0,0 +1,5 @@
+{
+  "semi": true,
+  "singleQuote": false,
+  "tabWidth": 2
+}
diff --git a/finance-tracker/app.js b/finance-tracker/app.js
index 7cfcd07..8c1068d 100644
--- a/finance-tracker/app.js
+++ b/finance-tracker/app.js
@@ -1,3 +1,45 @@
 // This is the entrypoint for your application.
 // node app.js
+// app.js
+import {printAllTransactions, addTransaction, getTransactionsByCategory, getTransactionsByDateRange, groupTransactionsByMonth, getAverageExpensePerCategory, removeTransactionById, findConsecutiveExpensiveMonths,} from "./finance.js";
 
+// Print data
+printAllTransactions();
+
+// Add one transaction
+addTransaction({
+  id: 6,
+  type: "expense",
+  category: "transport",
+  amount: 60,
+  description: "Train ticket",
+  date: "2026-02-02",
+});
+
+console.log("\nAfter adding one transaction:\n");
+printAllTransactions();
+
+// Filter by category 
+const foodTransactions = getTransactionsByCategory("food");
+console.log("\nFood transactions:", foodTransactions);
+
+//Bonus Challenges
+// Search transactions by date range using slice
+const februaryRange = getTransactionsByDateRange("2026-02-02", "2026-02-04");
+console.log("\nDate range 2026-02-02..2026-02-04:", februaryRange);
+
+// Group transactions by month using nested objects
+const groupedByMonth = groupTransactionsByMonth();
+console.log("\nGrouped by month:", groupedByMonth);
+
+// Calculate average expense per category
+const average = getAverageExpensePerCategory();
+console.log("\nAverage expense per category:", average);
+
+// Add ability to remove transactions by id
+const removedById = removeTransactionById(2);
+console.log("\nRemoved transaction with id=2:", removedById);
+
+// Create a function that finds consecutive expensive months
+const sequences = findConsecutiveExpensiveMonths(500);
+console.log("\nConsecutive expensive months (>= 500):", sequences);
\ No newline at end of file
diff --git a/finance-tracker/data.js b/finance-tracker/data.js
index d7863ff..8004dd4 100644
--- a/finance-tracker/data.js
+++ b/finance-tracker/data.js
@@ -1,2 +1,43 @@
 // Place here the transaction data array. Use it in your application as needed.
-const transactions = [];
\ No newline at end of file
+export const transactions = [
+    {
+    id: 1,
+    type: "income",
+    category: "salary",
+    amount: 3000,
+    description: "Monthly salary",
+    date: "2026-01-26",
+  },
+  {
+    id: 2,
+    type: "expense",
+    category: "food",
+    amount: 400,
+    description: "Groceries",
+    date: "2026-01-28",
+  },
+  {
+    id: 3,
+    type: "expense",
+    category: "housing",
+    amount: 1300,
+    description: "Rent",
+    date: "2026-01-27",
+  },
+  {
+    id: 4,
+    type: "income",
+    category: "side-income",
+    amount: 600,
+    description: "Freelance",
+    date: "2026-01-29",
+  },
+  {
+    id: 5,
+    type: "expense",
+    category: "bills",
+    amount: 250,
+    description: "Utilities",
+    date: "2026-01-30",
+  },
+];
diff --git a/finance-tracker/finance.js b/finance-tracker/finance.js
index ac2118f..7eb259b 100644
--- a/finance-tracker/finance.js
+++ b/finance-tracker/finance.js
@@ -1,27 +1,258 @@
-function addTransaction(transaction) {
-  // TODO: Implement this function
+// finance.js
+import chalk from "chalk";
+import { transactions } from "./data.js";
+
+// Format number 
+function formatEUR(amount) {
+  return `€${amount}`;
+}
+
+/*
+  1) addTransaction - Add new transaction to array
+  - Uses destructuring 
+  - Uses spread operator when pushing 
+*/
+export function addTransaction(transaction) {
+  const { id, type, category, amount, description, date } = transaction;
+  if ( id == null || !type || !category || amount == null || !description || !date ) {
+    console.log(chalk.red("❌ Missing required fields"));
+    return false;
+  }
+  transactions.push({ ...transaction });
+  return true;
+}
+
+/*
+  2) getTotalIncome()
+  - Sum income using a loop 
+*/
+export function getTotalIncome() {
+  let sum = 0;
+  for (const transaction of transactions) {
+    if (transaction.type === "income") {
+      sum += transaction.amount;
+    }
+  }
+  return sum;
+}
+
+/*
+  3) getTotalExpenses()
+  - Sum expenses using a loop
+*/
+export function getTotalExpenses() {
+  let sum = 0;
+  for (const transaction of transactions) {
+    if (transaction.type === "expense") {
+      sum = sum + transaction.amount;
+    }
+  }
+  return sum;
+}
+
+/*
+  4) getBalance() - Calculate total income minus expenses
+*/
+export function getBalance() {
+  return getTotalIncome() - getTotalExpenses();
 }
 
-function getTotalIncome() {
-  // TODO: Implement this function
+/*
+  5) getTransactionsByCategory(category) - Filter transactions
+  - Loop + push 
+*/
+export function getTransactionsByCategory(category) {
+  const result = [];
+  const target = category.toLowerCase();
+  for (const transaction of transactions) {
+    if (transaction.category.toLowerCase() === target) {
+      result.push(transaction);
+    }
+  }
+  return result;
 }
 
-function getTotalExpenses() {
-  // TODO: Implement this function
+/*
+  6) getLargestExpense() - Find highest expense amount
+*/
+export function getLargestExpense() {
+  let largest = null;
+  for (const transaction of transactions) {
+    if (transaction.type === "expense") {
+      if (largest === null || transaction.amount > largest.amount) {
+        largest = transaction;
+      }
+    }
+  }
+  return largest;
 }
 
-function getBalance() {
-  // TODO: Implement this function
+/*
+  7) printAllTransactions() - Display all transactions with formatting
+*/
+export function printAllTransactions() {
+  console.log(chalk.bold("💰 PERSONAL FINANCE TRACKER 💰"));
+  console.log("");
+  console.log(chalk.bold("All Transactions:"));
+  let i = 1;
+  for (const transaction of transactions) {
+    const { type, category, amount, description } = transaction;
+    const typeLabel = type.toUpperCase();
+    const categoryColored = chalk.yellow(category);
+    const amountText = formatEUR(amount);
+    const amountColored =
+      type === "income" ? chalk.green(amountText) : chalk.red(amountText);
+    console.log(
+      `${i}. [${typeLabel}] ${description} - ${amountColored} (${categoryColored})`
+    );
+
+    i = i + 1;  
+  }
+  const totalIncome = getTotalIncome();
+  const totalExpenses = getTotalExpenses();
+  const balance = getBalance();
+  const count = transactions.length;
+  const largestExpense = getLargestExpense();
+  console.log("");
+  console.log(chalk.bold("📊 FINANCIAL SUMMARY 📊"));
+
+  console.log(chalk.bold(`Total Income: ${chalk.green(formatEUR(totalIncome))}`));
+  console.log(
+    chalk.bold(`Total Expenses: ${chalk.red(formatEUR(totalExpenses))}`)
+  );
+  const balanceColored =
+    balance >= 0 ? chalk.cyan(formatEUR(balance)) : chalk.red(formatEUR(balance));
+  console.log(chalk.bold(`Current Balance: ${balanceColored}`));
+  console.log(chalk.bold(`Total Transactions: ${count}`));
+  if (largestExpense) {
+    console.log(
+      chalk.bold(
+        `Largest Expense: ${largestExpense.description} (${chalk.red(
+          formatEUR(largestExpense.amount)
+        )})`
+      )
+    );
+  } else {
+    console.log(chalk.bold("Largest Expense: none"));
+  }
+}
+
+/* Bonus Challenges*/
+
+/*
+  Bonus 1: Search transactions by date range using slice
+  - Copy + sort by date
+  - Find start and end indices
+  - Return slice(startIndex, endIndex+1)
+*/
+export function getTransactionsByDateRange(startDate, endDate) {
+  const sorted = [...transactions].sort((a, b) => a.date.localeCompare(b.date));
+  let startIndex = -1;
+  let endIndex = -1;
+  // Find first index with date >= startDate
+  for (let i = 0; i < sorted.length; i++) {
+    if (sorted[i].date >= startDate) {
+      startIndex = i;
+      break;
+    }
+  }
+  // Find last index with date <= endDate
+  for (let i = sorted.length - 1; i >= 0; i--) {
+    if (sorted[i].date <= endDate) {
+      endIndex = i;
+      break;
+    }
+  }
+  if (startIndex === -1 || endIndex === -1 || startIndex > endIndex) {
+    return [];
+  }
+  return sorted.slice(startIndex, endIndex + 1);
 }
 
-function getTransactionsByCategory(category) {
-  // TODO: Implement this function
+/*
+  Bonus 2: Group transactions by month using nested objects
+*/
+export function groupTransactionsByMonth() {
+  const groups = {};
+  for (const transaction of transactions) {
+    const month = transaction.date.slice(0, 7); // "YYYY-MM"
+    if (!groups[month]) {
+      groups[month] = { income: [], expense: [] };
+    }
+    if (transaction.type === "income") groups[month].income.push(transaction);
+    if (transaction.type === "expense") groups[month].expense.push(transaction);
+  }
+  return groups;
 }
 
-function getLargestExpense() {
-  // TODO: Implement this function
+/*
+  Bonus 3: Calculate average expense per category
+*/
+export function getAverageExpensePerCategory() {
+  const categorySumCount = {}; 
+  for (const transaction of transactions) {
+    if (transaction.type !== "expense") continue;
+    const c = transaction.category;
+    if (!categorySumCount[c]) categorySumCount[c] = { sum: 0, count: 0 };
+    categorySumCount[c].sum = categorySumCount[c].sum + transaction.amount;
+    categorySumCount[c].count = categorySumCount[c].count + 1;
+  }
+  const averages = {};
+  for (const category of Object.keys(categorySumCount)) {
+    averages[category] = categorySumCount[category].sum / categorySumCount[category].count;
+  }
+  return averages;
 }
 
-function printAllTransactions() {
-  // TODO: Implement this function
-}
\ No newline at end of file
+/*
+  Bonus 4: Remove transaction by id
+
+*/
+export function removeTransactionById(id) {
+  for (let i = 0; i < transactions.length; i++) {
+    if (transactions[i].id === id) {
+      const removed = transactions.splice(i, 1); // returns array of removed items
+      return removed[0];
+    }
+  }
+  return null;
+}
+
+/*
+  Bonus 5: Create a function that finds consecutive expensive months
+*/
+export function findConsecutiveExpensiveMonths(threshold) {
+  const groups = groupTransactionsByMonth();
+  const months = Object.keys(groups).sort(); // chronological order
+  // Build monthly expense totals
+  const monthlyExpense = {};
+  for (const month of months) {
+    let sum = 0;
+    for (const transaction of groups[month].expense) {
+      sum = sum + transaction.amount;
+    }
+    monthlyExpense[month] = sum;
+  }
+  const sequences = [];
+  let i = 0;
+  // while loop 
+  while (i < months.length) {
+    const month = months[i];
+    if (monthlyExpense[month] >= threshold) {
+      const seq = [month];
+      i = i + 1;
+      // Keep going while next months are also expensive
+      while (i < months.length && monthlyExpense[months[i]] >= threshold) {
+        seq.push(months[i]);
+        i = i + 1;
+      }
+      // Save only if sequence has at least 2 months 
+      if (seq.length >= 2) {
+        sequences.push(seq);
+      }
+    } else {
+      i = i + 1;
+    }
+  }
+  return sequences;
+}
diff --git a/finance-tracker/package-lock.json b/finance-tracker/package-lock.json
new file mode 100644
index 0000000..2195e5f
--- /dev/null
+++ b/finance-tracker/package-lock.json
@@ -0,0 +1,105 @@
+{
+  "name": "finance-tracker",
+  "version": "1.0.0",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "finance-tracker",
+      "version": "1.0.0",
+      "license": "ISC",
+      "dependencies": {
+        "chalk": "^4.1.2"
+      },
+      "devDependencies": {
+        "prettier": "^3.8.1"
+      }
+    },
+    "node_modules/ansi-styles": {
+      "version": "4.3.0",
+      "resolved": "https://registry.npmjs.org/ansi-styles/-/ansi-styles-4.3.0.tgz",
+      "integrity": "sha512-zbB9rCJAT1rbjiVDb2hqKFHNYLxgtk8NURxZ3IZwD3F6NtxbXZQCnnSi1Lkx+IDohdPlFp222wVALIheZJQSEg==",
+      "license": "MIT",
+      "dependencies": {
+        "color-convert": "^2.0.1"
+      },
+      "engines": {
+        "node": ">=8"
+      },
+      "funding": {
+        "url": "https://github.com/chalk/ansi-styles?sponsor=1"
+      }
+    },
+    "node_modules/chalk": {
+      "version": "4.1.2",
+      "resolved": "https://registry.npmjs.org/chalk/-/chalk-4.1.2.tgz",
+      "integrity": "sha512-oKnbhFyRIXpUuez8iBMmyEa4nbj4IOQyuhc/wy9kY7/WVPcwIO9VA668Pu8RkO7+0G76SLROeyw9CpQ061i4mA==",
+      "license": "MIT",
+      "dependencies": {
+        "ansi-styles": "^4.1.0",
+        "supports-color": "^7.1.0"
+      },
+      "engines": {
+        "node": ">=10"
+      },
+      "funding": {
+        "url": "https://github.com/chalk/chalk?sponsor=1"
+      }
+    },
+    "node_modules/color-convert": {
+      "version": "2.0.1",
+      "resolved": "https://registry.npmjs.org/color-convert/-/color-convert-2.0.1.tgz",
+      "integrity": "sha512-RRECPsj7iu/xb5oKYcsFHSppFNnsj/52OVTRKb4zP5onXwVF3zVmmToNcOfGC+CRDpfK/U584fMg38ZHCaElKQ==",
+      "license": "MIT",
+      "dependencies": {
+        "color-name": "~1.1.4"
+      },
+      "engines": {
+        "node": ">=7.0.0"
+      }
+    },
+    "node_modules/color-name": {
+      "version": "1.1.4",
+      "resolved": "https://registry.npmjs.org/color-name/-/color-name-1.1.4.tgz",
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+      "license": "MIT"
+    },
+    "node_modules/has-flag": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/has-flag/-/has-flag-4.0.0.tgz",
+      "integrity": "sha512-EykJT/Q1KjTWctppgIAgfSO0tKVuZUjhgMr17kqTumMl6Afv3EISleU7qZUzoXDFTAHTDC4NOoG/ZxU3EvlMPQ==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=8"
+      }
+    },
+    "node_modules/prettier": {
+      "version": "3.8.1",
+      "resolved": "https://registry.npmjs.org/prettier/-/prettier-3.8.1.tgz",
+      "integrity": "sha512-UOnG6LftzbdaHZcKoPFtOcCKztrQ57WkHDeRD9t/PTQtmT0NHSeWWepj6pS0z/N7+08BHFDQVUrfmfMRcZwbMg==",
+      "dev": true,
+      "license": "MIT",
+      "bin": {
+        "prettier": "bin/prettier.cjs"
+      },
+      "engines": {
+        "node": ">=14"
+      },
+      "funding": {
+        "url": "https://github.com/prettier/prettier?sponsor=1"
+      }
+    },
+    "node_modules/supports-color": {
+      "version": "7.2.0",
+      "resolved": "https://registry.npmjs.org/supports-color/-/supports-color-7.2.0.tgz",
+      "integrity": "sha512-qpCAvRl9stuOHveKsn7HncJRvv501qIacKzQlO/+Lwxc9+0q2wLyv4Dfvt80/DPn2pqOBsJdDiogXGR9+OvwRw==",
+      "license": "MIT",
+      "dependencies": {
+        "has-flag": "^4.0.0"
+      },
+      "engines": {
+        "node": ">=8"
+      }
+    }
+  }
+}
diff --git a/finance-tracker/package.json b/finance-tracker/package.json
new file mode 100644
index 0000000..5b85e7c
--- /dev/null
+++ b/finance-tracker/package.json
@@ -0,0 +1,16 @@
+{
+  "name": "finance-tracker",
+  "version": "1.0.0",
+  "description": "",
+  "type": "module",
+  "scripts": {
+    "start": "node app.js",
+    "format": "prettier --write ."
+  },
+  "dependencies": {
+    "chalk": "4.1.2"
+  },
+  "devDependencies": {
+    "prettier": "^3.8.1"
+  }
+}