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JavaScript Nested Loops — exercises and bug fixes

5 hands-on exercises and 5 find-the-bug challenges for the JavaScript Nested Loops lesson. Every one is checked automatically in the browser — write the code, run it, and the tests tell you what still fails.

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Exercises(5)

  1. 1

    Count the turns

    easy10 min

    Count how many times the inner code runs for a 3 by 4 pair of loops.

  2. 2

    Add up a grid

    easy10 min

    Add every number in the grid together and show the total.

  3. 3

    Build a star pattern

    easy10 min

    Build 3 rows of stars, where row 1 has one star. Join the rows with a dash.

  4. 4

    Pair two lists

    easy10 min

    Pair every name with every city and count how many pairs there are.

  5. 5

    Avoid repeating pairs

    medium10 min

    Count each pair of numbers only once by starting the inner loop after the outer one.

Find the bug(5)

  1. 1

    Fix the shared loop variable

    easy8 min

    Both loops use i, so the inner loop overwrites the outer one.

  2. 2

    Fix the inner loop that never runs

    easy8 min

    The inner loop starts above its limit, so nothing is added.

  3. 3

    Fix the row that is never reset

    easy8 min

    The row string carries over, so every row keeps the stars before it.

  4. 4

    Fix the break that stops too much

    easy8 min

    A break in the inner loop was meant to skip, not to end the pairing early.

  5. 5

    Fix the repeated pairs

    easy8 min

    The inner loop starts at zero, so every pair is counted twice.

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