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JavaScript Recursion — exercises and bug fixes

5 hands-on exercises and 5 find-the-bug challenges for the JavaScript Recursion 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 down

    easy10 min

    Count down from 3 to 1 with recursion, collecting the numbers joined by a dash.

  2. 2

    Factorial

    easy10 min

    Work out factorial of 5 with recursion.

  3. 3

    Add up an array

    easy10 min

    Add every number in the array using recursion.

  4. 4

    Count nested items

    easy10 min

    Count every item in a nested list, however deep it goes.

  5. 5

    Reverse a string

    medium10 min

    Reverse the word stream using recursion.

Find the bug(5)

  1. 1

    Fix the wrong base case

    easy8 min

    The base case returns the wrong starting value.

  2. 2

    Fix the value that never shrinks

    easy8 min

    The recursive call passes the same value, so nothing progresses.

  3. 3

    Fix the missing recursive call

    easy8 min

    Nested lists are counted as one item instead of being opened up.

  4. 4

    Fix the reversed join order

    easy8 min

    The characters are put back together the wrong way round.

  5. 5

    Fix the base case checked too late

    easy8 min

    The list is read before checking whether it is empty.

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