Labeled break and continue in Javascript - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested loops with labeled break

What is the output of this JavaScript code using a labeled break?

Javascript

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

A "1,1\n1,2\n2,1\n2,2\n3,1"

B "1,1\n1,2\n2,1"

C "1,1\n1,2\n2,1\n2,2"

D "1,1\n1,2\n1,3\n2,1\n2,2"

💡 Hint

Remember that labeled break exits the entire outer loop immediately.

The code prints pairs until i*j > 3. When i=2 and j=3, 2*3=6 > 3, so break outerLoop stops all loops. The last printed pair is 2,2.

❓ Predict Output

intermediate

Output of nested loops with labeled continue

What is the output of this JavaScript code using a labeled continue?

Javascript

outer: for (let i = 1; i <= 3; i++) {
  for (let j = 1; j <= 3; j++) {
    if (j === 2) {
      continue outer;
    }
    console.log(`${i},${j}`);
  }
}

A "1,1\n2,1\n3,1"

B "1,1\n1,3\n2,1\n2,3\n3,1\n3,3"

C "1,1\n1,3\n2,1\n3,1"

D "1,1\n2,1\n3,1\n3,3"

💡 Hint

Labeled continue skips to the next iteration of the outer loop.

When j equals 2, continue outer skips the rest of the inner loop and goes to the next i. So only j=1 is printed for each i.

🔧 Debug

advanced

Identify the error with labeled continue usage

What error does this JavaScript code produce?

Javascript

outer: for (let i = 0; i < 2; i++) {
  for (let j = 0; j < 2; j++) {
    if (j === 1) {
      continue inner;
    }
    console.log(i, j);
  }
}

A SyntaxError: Unexpected identifier

B ReferenceError: inner is not defined

C No error, outputs: 0 0 1 0

D TypeError: continue label must be an identifier

💡 Hint

Check if the label used in continue exists.

The label 'inner' is not defined anywhere, so using 'continue inner;' causes a ReferenceError.

❓ Predict Output

advanced

Output with nested labeled break and continue

What is the output of this JavaScript code?

Javascript

outer: for (let i = 1; i <= 3; i++) {
  inner: for (let j = 1; j <= 3; j++) {
    if (i === j) {
      continue outer;
    }
    if (i + j === 4) {
      break inner;
    }
    console.log(`${i},${j}`);
  }
}

A "1,2\n2,1\n3,1\n3,2"

B "1,2\n1,3\n2,1\n3,1\n3,2"

C "1,2\n2,1\n3,1"

D "1,2\n2,1\n3,2"

💡 Hint

Remember continue outer skips to next i, break inner exits inner loop.

When i===j, continue outer skips to next i. When i+j===4, break inner exits inner loop. The printed pairs are 1,2 then next i=2, j=1 then i=3, j=1 and j=2.

🧠 Conceptual

expert

Effect of labeled break on loop execution

Consider this code snippet:

label1: for (let a = 0; a < 2; a++) {
  label2: for (let b = 0; b < 2; b++) {
    if (a === b) {
      break label1;
    }
    console.log(a, b);
  }
}

What is the value of variable a after the loops finish?

A 1

B undefined

C 2

D 0

💡 Hint

Labeled break exits the outer loop immediately when condition is met.

The break label1 stops the outer loop when a === b (which is true at a=0,b=0). The outer loop ends immediately, so a remains 0 after the loops finish.

Practice

1.

What does the break label; statement do in JavaScript?

easy

A. It exits the loop identified by the label immediately.

B. It skips the current iteration of the inner loop only.

C. It restarts the entire program from the beginning.

D. It pauses the loop until a condition is met.

Solution

1. Step 1: Understand labeled break

   The break label; statement exits the loop that has the specified label, not just the innermost loop.

2. Step 2: Compare with normal break

   Normal break exits only the current loop, but labeled break exits the labeled outer loop immediately.

3. Final Answer:

   It exits the loop identified by the label immediately. -> Option A

4. Quick Check:

   break label exits labeled loop [OK]

Hint: Labeled break exits the named loop, not just inner loop [OK]

Common Mistakes:

• Thinking break label only skips current iteration
• Confusing break label with continue label
• Assuming break label pauses the loop

2.

Which of the following is the correct syntax to continue the outer loop labeled outerLoop?

outerLoop: for(let i = 0; i < 3; i++) {
  for(let j = 0; j < 3; j++) {
    // What goes here?
  }
}

easy

A. continue outerLoop;

B. continue (outerLoop);

C. continue: outerLoop;

D. continue to outerLoop;

Solution

1. Step 1: Recall labeled continue syntax

   The correct syntax to continue a labeled loop is continue labelName; without parentheses or extra words.

2. Step 2: Match options with syntax

   continue outerLoop; matches the correct syntax exactly. Options B, C, and D are invalid syntax.

3. Final Answer:

   continue outerLoop; -> Option A

4. Quick Check:

   continue labelName; is correct syntax [OK]

Hint: Use 'continue label;' exactly, no parentheses or colons [OK]

Common Mistakes:

• Adding parentheses around label
• Using colon after continue
• Writing extra words like 'to'

3.

What is the output of the following code?

outer: for(let i = 1; i <= 3; i++) {
  for(let j = 1; j <= 3; j++) {
    if(j === 2) continue outer;
    console.log(i, j);
  }
}

medium

A. 1 1
1 3
2 1
3 1

B. 1 1
2 1
3 1

C. 1 1
1 3
2 1
2 3
3 1
3 3

D. 1 1
2 2
3 3

Solution

1. Step 1: Understand continue outer;

   When j === 2, continue outer; skips to the next iteration of the outer loop, skipping the rest of inner loop and console.log for that i.

2. Step 2: Trace iterations

   For i=1: j=1 logs '1 1', j=2 triggers continue outer (skip to i=2). For i=2: j=1 logs '2 1', j=2 triggers continue outer (skip to i=3). For i=3: j=1 logs '3 1', j=2 triggers continue outer (loop ends after i=3).

3. Final Answer:

   1 1 2 1 3 1 -> Option B

4. Quick Check:

   continue outer skips inner loop rest [OK]

Hint: continue label skips to next outer loop iteration [OK]

Common Mistakes:

• Thinking continue outer skips only inner iteration
• Expecting all inner loop logs
• Confusing break and continue effects

4.

Find the error in this code snippet:

outerLoop: for(let i = 0; i < 2; i++) {
  for(let j = 0; j < 2; j++) {
    if(i === j) break;
    if(j === 1) continue outerLoop;
    console.log(i, j);
  }
}

medium

A. The label name is missing a colon.

B. Using continue outerLoop; inside inner loop is invalid.

C. The break; statement breaks only inner loop, not labeled loop.

D. No error; code runs correctly.

Solution

1. Step 1: Analyze break statement

   The break; without label breaks only the innermost loop, not the labeled outer loop.

2. Step 2: Check labeled continue usage

   The continue outerLoop; is valid and skips to next iteration of the labeled loop.

3. Final Answer:

   The break; statement breaks only inner loop, not labeled loop. -> Option C

4. Quick Check:

   break without label affects inner loop only [OK]

Hint: break without label breaks inner loop only [OK]

Common Mistakes:

• Assuming break breaks labeled loop without label
• Thinking continue outerLoop is invalid
• Confusing label syntax

5.

Given the nested loops below, how can you skip all remaining iterations of the outer loop when j === 3?

outerLoop: for(let i = 1; i <= 5; i++) {
  for(let j = 1; j <= 5; j++) {
    if(j === 3) {
      // What statement here?
    }
    console.log(i, j);
  }
}

hard

A. continue outerLoop;

B. break;

C. continue;

D. break outerLoop;

Solution

1. Step 1: Understand the goal

   We want to stop all remaining iterations of the outer loop when j === 3, meaning exit the outer loop completely.

2. Step 2: Choose correct statement

   break outerLoop; exits the labeled outer loop immediately. Plain break; exits only inner loop. continue; and continue outerLoop; skip iterations but do not exit the outer loop.

3. Final Answer:

   break outerLoop; -> Option D

4. Quick Check:

   break label exits labeled loop [OK]

Hint: Use break label to exit outer loop immediately [OK]

Common Mistakes:

• Using break without label to exit outer loop
• Using continue instead of break
• Confusing continue label with break label