Function Mastery — Solutions

Jun 2026

JavaScript, Functions, Solutions

Syifa Fauziyah Arizal

This page contains the official solutions for Module 4. If you haven’t tried the challenges yet — stop scrolling.

“Copying solutions doesn’t make you better. Understanding why they work does.”

🔥 Challenge 1 — Even or Odd Function

Create a function that:

Receives a number
Returns Even or Odd

JavaScript


function checkEvenOdd(number) {
  if (number % 2 === 0) {
    return "Even";
  } else {
    return "Odd";
  }
}

console.log(checkEvenOdd(7));
console.log(checkEvenOdd(10));

Modulo (%) is the core logic here. Same weapon, different use case.

🔥 Challenge 2 — Grade Generator

Rules:

Input score
Return grade (A–E)

JavaScript


function getGrade(score) {
  if (score >= 90) return "A";
  if (score >= 80) return "B";
  if (score >= 70) return "C";
  if (score >= 60) return "D";
  return "E";
}

console.log(getGrade(92));
console.log(getGrade(76));
console.log(getGrade(60));

Early return keeps logic clean and readable. No nested mess.

🔥 Challenge 3 — Login Function

Conditions:

Username must match
Password must match
Return success or error message

JavaScript


function login(username, password) {
  const correctUsername = "admin";
  const correctPassword = "12345";

  if (username === correctUsername && password === correctPassword) {
    return "Login successful 👋";
  } else {
    return "Invalid credentials ❌";
  }
}

console.log(login("admin", "12345"));
console.log(login("user", "123"));

This is simplified authentication logic. Same concept used in real apps.

🚀 Bonus — Cleaner Validation

More detailed feedback:

JavaScript


function login(username, password) {
  if (username !== "admin") {
    return "Username not found";
  } else if (password !== "12345") {
    return "Wrong password";
  } else {
    return "Login successful";
  }
}

Same logic. Better UX.