Why loop control is required in Javascript - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this loop with break?

Consider the following JavaScript code. What will it print to the console?

Javascript

for (let i = 0; i < 5; i++) {
  if (i === 3) {
    break;
  }
  console.log(i);
}

A 0 1 2

B 0 1 2 3 4

C 3 4

D 0 1 2 3

💡 Hint

The break statement stops the loop immediately when the condition is met.

The loop starts from 0 and prints each number. When i equals 3, the break stops the loop, so 3 and 4 are not printed.

❓ Predict Output

intermediate

What does continue do in this loop?

Look at this code. What numbers will be printed?

Javascript

for (let i = 0; i < 5; i++) {
  if (i === 2) {
    continue;
  }
  console.log(i);
}

A 0 1 3 4

B 0 1 2 3 4

C 0 1 2 3

D 2

💡 Hint

The continue statement skips the current loop iteration when the condition is true.

When i is 2, continue skips the console.log for that iteration, so 2 is not printed.

🧠 Conceptual

advanced

Why is loop control important?

Why do we need loop control statements like break and continue in loops?

A To make the loop run forever without stopping.

B To stop or skip parts of the loop based on conditions, preventing infinite loops or unwanted actions.

C To automatically increase the loop counter by 2 each time.

D To print all values without any condition.

💡 Hint

Think about how loops can be controlled to avoid problems or to skip some steps.

Loop control statements help manage how loops run, allowing us to stop early or skip certain steps, which is useful for efficiency and correctness.

❓ Predict Output

advanced

What happens without loop control in this code?

What will happen when this code runs?

Javascript

let i = 0;
while (i < 5) {
  console.log(i);
  // missing i++ here
}

A It prints 0 to 4 and stops.

B It throws a syntax error.

C It prints 0 forever (infinite loop).

D It prints nothing.

💡 Hint

Think about what happens if the loop variable never changes.

Since i never increases, the condition i < 5 is always true, so the loop never ends and keeps printing 0.

❓ Predict Output

expert

What is the output with nested loops and break?

What will this code print to the console?

Javascript

for (let i = 0; i < 3; i++) {
  for (let j = 0; j < 3; j++) {
    if (j === 1) {
      break;
    }
    console.log(`i=${i}, j=${j}`);
  }
}

A

i=0, j=0
i=0, j=1
i=1, j=0
i=2, j=0

B

i=0, j=0
i=0, j=1
i=1, j=0
i=1, j=1
i=2, j=0
i=2, j=1

C

i=0, j=0
i=0, j=1
i=0, j=2
i=1, j=0
i=1, j=1
i=1, j=2
i=2, j=0
i=2, j=1
i=2, j=2

D

i=0, j=0
i=1, j=0
i=2, j=0

💡 Hint

The break stops the inner loop when j equals 1, so only j=0 prints each time.

For each i, the inner loop runs j from 0 to 2, but breaks when j is 1, so only j=0 is printed per i.