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JavaScript Array concat and join — exercises and bug fixes

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

    Join two arrays

    easy10 min

    Combine two arrays with concat and show the result joined by commas.

  2. 2

    Combine with spread

    easy10 min

    Combine two arrays using spread instead of concat.

  3. 3

    Choose a separator

    easy10 min

    Join a list of words using a space, the word and, and another space.

  4. 4

    Glue letters together

    easy10 min

    Join an array of letters with no separator at all.

  5. 5

    Join three arrays

    medium10 min

    Concat three arrays in one call and show the total length.

Find the bug(5)

  1. 1

    Fix concat that was thrown away

    easy8 min

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

  2. 2

    Fix the array pushed instead of joined

    easy8 min

    Pushing an array adds it as a single nested element.

  3. 3

    Fix the wrong separator

    easy8 min

    The list should read as a sentence, not a comma list.

  4. 4

    Fix join called without a separator

    easy8 min

    The default separator adds commas between the letters.

  5. 5

    Fix the spread that was missed

    easy8 min

    Without spread the arrays end up nested instead of merged.

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