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JavaScript Array flat — exercises and bug fixes

5 hands-on exercises and 5 find-the-bug challenges for the JavaScript Array flat 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

    Flatten one level

    easy10 min

    Flatten a nested array and join the result with commas.

  2. 2

    Flatten two levels

    easy10 min

    Flatten an array nested two deep and show the length.

  3. 3

    Flatten completely

    easy10 min

    Use Infinity to flatten however deep the nesting goes.

  4. 4

    Split into words

    easy10 min

    Use flatMap to split each sentence into words and join with commas.

  5. 5

    Merge groups of names

    medium10 min

    Flatten an array of groups and show the total number of people.

Find the bug(5)

  1. 1

    Fix the default depth

    easy8 min

    One level is not enough for an array nested two deep.

  2. 2

    Fix map used instead of flatMap

    easy8 min

    map leaves each result nested inside its own array.

  3. 3

    Fix the result of flat being ignored

    easy8 min

    flat returns a new array; it does not change the original.

  4. 4

    Fix the fixed depth on unknown nesting

    easy8 min

    The nesting is deeper than the depth given.

  5. 5

    Fix concat used on nested groups

    easy8 min

    The groups need flattening into one list of people.

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