6. Conditional Statements

1. Check Positive, Negative, or Zero

Program 1: Fixed Value

				
					<script>
let num = -5;

if (num > 0)
  document.write("Positive");
else if (num < 0)
  document.write("Negative");
else
  document.write("Zero");
</script>

Program 2: User Input

				
					<script>
let num = Number(prompt("Enter a number"));

if (num > 0)
  alert("Positive");
else if (num < 0)
  alert("Negative");
else
  alert("Zero");
</script>

2. Find Largest of Two Numbers

Program 1: Using if–else

				
					<script>
let a = 10, b = 20;

if (a > b)
  document.write(a + " is larger");
else
  document.write(b + " is larger");
</script>

Program 2: Using Ternary Operator

				
					<script>
let a = 15, b = 7;
document.write(a > b ? a + " is larger" : b + " is larger");
</script>

3. Find Largest of Three Numbers

Program 1: Using if–else

				
					<script>
let a = 10, b = 25, c = 15;

if (a > b && a > c)
  document.write(a + " is largest");
else if (b > c)
  document.write(b + " is largest");
else
  document.write(c + " is largest");
</script>

Program 2: Using Math.max()

				
					<script>
let a = 5, b = 12, c = 9;
document.write(Math.max(a, b, c) + " is largest");
</script>

4. Check Voting Eligibility

Program 1: Fixed Age

				
					<script>
let age = 20;

if (age >= 18)
  document.write("Eligible to vote");
else
  document.write("Not eligible to vote");
</script>

Program 2: User Input

				
					<script>
let age = Number(prompt("Enter your age"));
alert(age >= 18 ? "Eligible to vote" : "Not eligible");
</script>

5. Student Grade System

Program 1: Marks to Grade

				
					<script>
let marks = 78;

if (marks >= 90)
  document.write("Grade A");
else if (marks >= 75)
  document.write("Grade B");
else if (marks >= 60)
  document.write("Grade C");
else
  document.write("Fail");
</script>

Program 2: User Input

				
					<script>
let marks = Number(prompt("Enter marks"));

if (marks >= 40)
  alert("Pass");
else
  alert("Fail");
</script>

6. Simple Login Validation

Program 1: Fixed Credentials

				
					<script>
let username = "admin";
let password = "1234";

if (username === "admin" && password === "1234")
  document.write("Login successful");
else
  document.write("Invalid credentials");
</script>

Program 2: User Input Login

				
					<script>
let user = prompt("Enter username");
let pass = prompt("Enter password");

if (user === "admin" && pass === "admin123")
  alert("Login successful");
else
  alert("Login failed");
</script>

7. Check Leap Year

Program 1: Fixed Year

				
					<script>
let year = 2024;

if ((year % 4 === 0 && year % 100 !== 0) || year % 400 === 0)
  document.write("Leap Year");
else
  document.write("Not a Leap Year");
</script>

Program 2: User Input

				
					<script>
let year = Number(prompt("Enter year"));
alert(
  ((year % 4 === 0 && year % 100 !== 0) || year % 400 === 0)
  ? "Leap Year"
  : "Not a Leap Year"
);
</script>

8. Day of Week Using switch

Program 1: Fixed Day Number

				
					<script>
let day = 3;

switch (day) {
  case 1: document.write("Monday"); break;
  case 2: document.write("Tuesday"); break;
  case 3: document.write("Wednesday"); break;
  case 4: document.write("Thursday"); break;
  case 5: document.write("Friday"); break;
  case 6: document.write("Saturday"); break;
  case 7: document.write("Sunday"); break;
  default: document.write("Invalid day");
}
</script>

Program 2: User Input

				
					<script>
let day = Number(prompt("Enter day number"));
switch (day) {
  case 1: alert("Monday"); break;
  case 2: alert("Tuesday"); break;
  default: alert("Invalid day");
}
</script>

9. Month Name Using switch

Program 1: Fixed Month

				
					<script>
let month = 5;

switch (month) {
  case 1: document.write("January"); break;
  case 2: document.write("February"); break;
  case 3: document.write("March"); break;
  case 4: document.write("April"); break;
  case 5: document.write("May"); break;
  default: document.write("Invalid month");
}
</script>

Program 2: User Input

				
					<script>
let month = Number(prompt("Enter month number"));
switch (month) {
  case 12: alert("December"); break;
  default: alert("Invalid month");
}
</script>

10. Calculator Using switch

Program 1: Fixed Values

				
					<script>
let a = 10, b = 5, op = "+";

switch (op) {
  case "+": document.write(a + b); break;
  case "-": document.write(a - b); break;
  case "*": document.write(a * b); break;
  case "/": document.write(a / b); break;
  default: document.write("Invalid operator");
}
</script>

Program 2: User Input Calculator

				
					<script>
let a = Number(prompt("Enter first number"));
let b = Number(prompt("Enter second number"));
let op = prompt("Enter operator (+ - * /)");

switch (op) {
  case "+": alert(a + b); break;
  case "-": alert(a - b); break;
  case "*": alert(a * b); break;
  case "/": alert(a / b); break;
  default: alert("Invalid operator");
}
</script>