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Career, Salary, Scope & Benefits GuideJavaScript Break Statement Tutorial – Complete Guide with ExamplesJavaScript Break and Continue Statements – Complete Guide with ExamplesJavaScript Continue Statement Tutorial – Skip Iterations with ExamplesJavaScript Do While Loop Tutorial – Execute at Least Once with ExamplesJavaScript Do-While Loop Tutorial – Complete Guide with ExamplesJavaScript For Loop Tutorial – Complete Guide with ExamplesJavaScript If Statement Tutorial – Conditional Logic with ExamplesJavaScript If Else Statement Tutorial – Complete Guide with ExamplesJavaScript If Statement Tutorial – Complete Guide with ExamplesJavaScript Nested If Statement Tutorial – Multi-Level Conditions with ExamplesNested Loops in JavaScriptJavaScript Control Flow Practice Programs – 20+ Exercises with SolutionsJavaScript Switch Statement Tutorial – Case Matching with ExamplesSwitch Statement in JavaScriptJavaScript While Loop Tutorial – Complete Guide with ExamplesJavaScript Arrow Functions Tutorial – Syntax, Use Cases & this BindingJavaScript Callback Functions Explained – Synchronous & AsynchronousJavaScript Closures Explained – Lexical Scope, Private State & MemoryJavaScript Function Declaration Tutorial – Hoisting, Syntax & ScopeJavaScript Function Expression Tutorial – Anonymous, Named & AssignedJavaScript Higher Order Functions Tutorial – map, filter, reduce & Custom HOFsJavaScript IIFE Explained – Immediately Invoked Function ExpressionJavaScript Functions Practice Programs – 20+ Exercises with SolutionsJavaScript Recursion Tutorial – Call Stack, Base Case & Recursive PatternsJavaScript Array Basics - 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Practice JavaScript control flow with 20+ programs covering if-else, loops, switch, break, and continue. Each exercise has a clear problem statement, solution, and output.
This chapter contains 20+ practice programs covering all control flow topics: if-else, switch, for loop, while loop, do-while, break, and continue. Each program has a clear problem statement, solution code, and expected output.
Work through these to solidify your understanding!
Program 2: Positive, Negative, or Zero
javascript example
let n = -5;
if (n > 0) {
console.log(n + " is Positive");
} else if (n < 0) {
console.log(n + " is Negative");
} else {
console.log("The number is Zero");
}Output
-5 is Negative
Program 3: Largest of Three Numbers
javascript example
let a = 45, b = 78, c = 62;
let largest;
if (a >= b && a >= c) {
largest = a;
} else if (b >= a && b >= c) {
largest = b;
} else {
largest = c;
}
console.log(`Numbers: ${a}, ${b}, ${c}`);
console.log("Largest:", largest);Output
Numbers: 45, 78, 62 Largest: 78
Program 4: Factorial Using For Loop
Example
let num = 6;
let factorial = 1;
for (let i = 1; i <= num; i++) {
factorial *= i;
}
console.log(`${num}! = ${factorial}`);
Output
6! = 720
Program 5: Fibonacci Series (First N Terms)
Example
let n = 10;
let a = 0, b = 1;
console.log(`First ${n} Fibonacci numbers:`);
process.stdout.write(a + " " + b + " ");
for (let i = 3; i <= n; i++) {
let c = a + b;
process.stdout.write(c + " ");
a = b;
b = c;
}
console.log();
Output
First 10 Fibonacci numbers: 0 1 1 2 3 5 8 13 21 34
Program 6: Prime Number Check
Example
function isPrime(num) {
if (num < 2) return false;
for (let i = 2; i <= Math.sqrt(num); i++) {
if (num % i === 0) return false;
}
return true;
}
let number = 29;
if (isPrime(number)) {
console.log(number + " is a PRIME number");
} else {
console.log(number + " is NOT a prime number");
}
Output
29 is a PRIME number
Program 7: Sum of Digits
javascript example
let num = 9876;
let sum = 0;
let temp = num;
while (temp > 0) {
sum += temp % 10;
temp = Math.floor(temp / 10);
}
console.log(`Sum of digits of ${num} = ${sum}`);Output
Sum of digits of 9876 = 30
Program 8: Reverse a Number
javascript example
let original = 54321;
let reversed = 0;
let temp = original;
while (temp > 0) {
reversed = reversed * 10 + (temp % 10);
temp = Math.floor(temp / 10);
}
console.log("Original:", original);
console.log("Reversed:", reversed);Output
Original: 54321 Reversed: 12345
Program 9: Armstrong Number Check
An Armstrong number equals the sum of its own digits each raised to the power of the number of digits.
javascript example
let num = 153;
let temp = num;
let sum = 0;
let digits = String(num).length;
while (temp > 0) {
let digit = temp % 10;
sum += Math.pow(digit, digits);
temp = Math.floor(temp / 10);
}
if (sum === num) {
console.log(num + " is an Armstrong number ✓");
console.log("Proof: 1³ + 5³ + 3³ =", 1 + 125 + 27);
} else {
console.log(num + " is NOT an Armstrong number");
}Output
153 is an Armstrong number ✓ Proof: 1³ + 5³ + 3³ = 153
Program 10: Palindrome Number Check
javascript example
let num = 12321;
let original = num;
let reversed = 0;
let temp = num;
while (temp > 0) {
reversed = reversed * 10 + (temp % 10);
temp = Math.floor(temp / 10);
}
if (original === reversed) {
console.log(original + " is a PALINDROME ✓");
} else {
console.log(original + " is NOT a palindrome");
}Output
12321 is a PALINDROME ✓
Program 11: Leap Year Check
javascript example
let year = 2024;
if (year % 400 === 0) {
console.log(year + " is a leap year (divisible by 400)");
} else if (year % 100 === 0) {
console.log(year + " is NOT a leap year (divisible by 100, not 400)");
} else if (year % 4 === 0) {
console.log(year + " is a leap year (divisible by 4)");
} else {
console.log(year + " is NOT a leap year");
}Output
2024 is a leap year (divisible by 4)
📐 Pattern Programs
Program 12: Right Triangle Star Pattern
Example
let rows = 5;
for (let i = 1; i <= rows; i++) {
let stars = "";
for (let j = 1; j <= i; j++) {
stars += "* ";
}
console.log(stars);
}
Output
* * * * * * * * * * * * * * *
Program 13: Inverted Triangle
Example
let n = 5;
for (let i = n; i >= 1; i--) {
let stars = "";
for (let j = 1; j <= i; j++) {
stars += "* ";
}
console.log(stars);
}
Output
* * * * * * * * * * * * * * *
Program 14: Number Pattern (Floyd's Triangle)
Example
let rows = 5;
let num = 1;
for (let i = 1; i <= rows; i++) {
let row = "";
for (let j = 1; j <= i; j++) {
row += num + "\t";
num++;
}
console.log(row);
}
Output
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Program 15: Multiplication Table
Example
let table = 7;
console.log(`--- Multiplication Table of ${table} ---`);
for (let i = 1; i <= 10; i++) {
console.log(`${table} × ${i} = ${table * i}`);
}
Output
--- Multiplication Table of 7 --- 7 × 1 = 7 7 × 2 = 14 7 × 3 = 21 7 × 4 = 28 7 × 5 = 35 7 × 6 = 42 7 × 7 = 49 7 × 8 = 56 7 × 9 = 63 7 × 10 = 70
🔤 String Programs
Program 16: Palindrome String Check
Example
function isPalindromeStr(str) {
str = str.toLowerCase().replace(/[^a-z0-9]/g, "");
let n = str.length;
for (let i = 0; i < Math.floor(n / 2); i++) {
if (str[i] !== str[n - 1 - i]) return false;
}
return true;
}
let words = ["radar", "hello", "madam", "javascript", "level"];
for (let word of words) {
let result = isPalindromeStr(word) ? "PALINDROME ✓" : "not palindrome";
console.log(`"${word}" → ${result}`);
}
Output
"radar" → PALINDROME ✓ "hello" → not palindrome "madam" → PALINDROME ✓ "javascript" → not palindrome "level" → PALINDROME ✓
Program 17: Count Vowels and Consonants
Example
let str = "Hello World";
let vowels = 0, consonants = 0;
for (let char of str.toLowerCase()) {
if (char >= 'a' && char <= 'z') {
if ("aeiou".includes(char)) {
vowels++;
} else {
consonants++;
}
}
}
console.log(`String: "${str}"`);
console.log("Vowels:", vowels);
console.log("Consonants:", consonants);
Output
String: "Hello World" Vowels: 3 Consonants: 7
🔀 Break and Continue Programs
Program 18: Find First Element Greater Than 50
Example
let numbers = [12, 34, 48, 56, 72, 89];
let found = -1;
for (let i = 0; i < numbers.length; i++) {
if (numbers[i] > 50) {
found = numbers[i];
console.log(`First number > 50: ${found} (at index ${i})`);
break;
}
}
if (found === -1) {
console.log("No number greater than 50 found");
}
Output
First number > 50: 56 (at index 3)
Program 19: Print All Odd Numbers Using Continue
Example
console.log("Odd numbers from 1 to 20:");
let result = "";
for (let i = 1; i <= 20; i++) {
if (i % 2 === 0) continue;
result += i + " ";
}
console.log(result);
Output
Odd numbers from 1 to 20: 1 3 5 7 9 11 13 15 17 19
🔄 Do-While Programs
Program 20: Guess the Number (Simulation)
Example
let secret = 42;
let guesses = [10, 60, 42]; // simulated user guesses
let attempt = 0;
let guess;
do {
guess = guesses[attempt];
attempt++;
console.log(`Attempt ${attempt}: Guessed ${guess}`);
if (guess < secret) {
console.log(" → Too low!");
} else if (guess > secret) {
console.log(" → Too high!");
} else {
console.log(` → Correct! 🎉 Found in ${attempt} attempts`);
}
} while (guess !== secret);
Output
Attempt 1: Guessed 10 → Too low! Attempt 2: Guessed 60 → Too high! Attempt 3: Guessed 42 → Correct! 🎉 Found in 3 attempts
🧩 Challenge Programs
Challenge 1: Find All Prime Numbers Up to N
Example
let n = 30;
let primes = [];
for (let num = 2; num <= n; num++) {
let isPrime = true;
for (let i = 2; i <= Math.sqrt(num); i++) {
if (num % i === 0) {
isPrime = false;
break;
}
}
if (isPrime) primes.push(num);
}
console.log(`Prime numbers up to ${n}:`);
console.log(primes.join(", "));
console.log("Count:", primes.length);
Output
Prime numbers up to 30: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29 Count: 10
Challenge 2: Grade Calculator for Multiple Students
Example
let students = [
{ name: "Alice", score: 92 },
{ name: "Bob", score: 75 },
{ name: "Charlie", score: 58 },
{ name: "Diana", score: 88 },
{ name: "Eve", score: 45 }
];
function getGrade(score) {
if (score >= 90) return "A+";
else if (score >= 80) return "A";
else if (score >= 70) return "B";
else if (score >= 60) return "C";
else if (score >= 50) return "D";
else return "F";
}
console.log("Student Results:");
console.log("────────────────────────────");
for (let student of students) {
let grade = getGrade(student.score);
let status = student.score >= 50 ? "PASS" : "FAIL";
console.log(`${student.name.padEnd(10)} | ${student.score} | ${grade} | ${status}`);
}
Output
Student Results: ──────────────────────────── Alice | 92 | A+ | PASS Bob | 75 | B | PASS Charlie | 58 | C | PASS Diana | 88 | A | PASS Eve | 45 | F | FAIL
Challenge 3: FizzBuzz (Classic Interview Program)
Example
for (let i = 1; i <= 30; i++) {
let output = "";
if (i % 3 === 0) output += "Fizz";
if (i % 5 === 0) output += "Buzz";
console.log(output || i);
}
Output
1 2 Fizz 4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz 16 17 Fizz 19 Buzz Fizz 22 23 Fizz Buzz 26 Fizz 28 29 FizzBuzz
🎤 Interview Questions
Q1. What is FizzBuzz and why is it asked in interviews? > FizzBuzz tests basic programming logic, loop understanding, and condition handling. Print numbers 1 to N, replacing multiples of 3 with "Fizz", multiples of 5 with "Buzz", and multiples of both with "FizzBuzz".
Q2. How do you find if a number is prime? > Check if any number from 2 to √n divides n evenly. If none does, it's prime. Checking only up to √n is an optimization — if n has a factor larger than √n, it must also have one smaller than √n.
Q3. What is an Armstrong number? > A number where the sum of its digits raised to the power of the number of digits equals the number itself. Example: 153 = 1³ + 5³ + 3³ = 1 + 125 + 27 = 153.
Q4. How do you check if a string is a palindrome? > Compare characters from both ends toward the middle. If all pairs match, it's a palindrome. Alternatively, reverse the string and check if it equals the original.
Q5. Write a program to print the first 10 Fibonacci numbers. > Start with 0 and 1, then each subsequent number is the sum of the previous two: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34.
🔑 Key Takeaways
| Topic | Programs to Master |
|---|---|
| if-else | Even/odd, positive/negative, grade calculator |
| Nested if | Loan check, multi-criteria validation |
| switch | Calculator, day/month, role-based logic |
| for loop | Factorial, Fibonacci, patterns, multiplication table |
| while loop | Digit sum, reverse, GCD |
| do-while | Menu, input validation, game loop |
| break | Search (find first), stop on condition |
| continue | Filter (skip certain values), data cleaning |
💡 Practice tip: Try to solve each program on your own first, then check the solution. The struggle is where learning happens!
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