While loop in Javascript - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple while loop

What will be the output of the following JavaScript code?

Javascript

let count = 0;
let result = '';
while (count < 3) {
  result += count + '-';
  count++;
}
console.log(result);

A "0-1-2-3-"

B "0-1-2-"

C "1-2-3-"

D "-0-1-2"

💡 Hint

Remember the loop runs while count is less than 3, and count starts at 0.

The loop runs while count is 0, 1, and 2. Each time it adds the current count and a dash. When count reaches 3, the loop stops, so '0-1-2-' is printed.

❓ Predict Output

intermediate

While loop with break statement

What will be printed by this code?

Javascript

let i = 1;
let output = '';
while (i <= 5) {
  if (i === 3) break;
  output += i;
  i++;
}
console.log(output);

A "12345"

B "123"

C ""

D "12"

💡 Hint

The loop stops when i equals 3.

The loop adds '1' and '2' to output. When i becomes 3, the break stops the loop before adding '3'. So output is '12'.

❓ Predict Output

advanced

While loop with nested condition

What is the final value of variable sum after running this code?

Javascript

let n = 5;
let sum = 0;
while (n > 0) {
  if (n % 2 === 0) {
    sum += n;
  }
  n--;
}

A 8

B 10

C 6

D 0

💡 Hint

Add only even numbers from 5 down to 1.

Even numbers between 5 and 1 are 4 and 2. Their sum is 6.

❓ Predict Output

advanced

While loop with post-increment in condition

What will this code output?

Javascript

let x = 0;
let output = '';
while (x++ < 3) {
  output += x;
}
console.log(output);

A "123"

B "234"

C "1234"

D "012"

💡 Hint

Remember x++ returns the value before incrementing.

The condition checks x before incrementing. Loop runs while x is 0,1,2. Inside loop, x is incremented, so output adds 1,2,3.

❓ Predict Output

expert

While loop with complex condition and variable update

What is the output of this code snippet?

Javascript

let a = 1;
let b = 10;
let result = '';
while (a < b) {
  result += a + ',';
  a *= 2;
  b -= 3;
}
console.log(result);

A "1,2,"

B "1,2,4,8,"

C "1,2,4,"

D "1,2,4,8,16,"

💡 Hint

Check how a and b change each loop and when the condition fails.

Loop 1: a=1,b=10 (1<10) add '1,'; a=2,b=7 Loop 2: a=2,b=7 (2<7) add '2,'; a=4,b=4 Condition: a=4,b=4 (4<4) false, stop. So output is '1,2,'