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JavaScript Array forEach — exercises and bug fixes

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

    Build a string with forEach

    easy10 min

    Use forEach to build a dash-separated string of the values.

  2. 2

    Add up with forEach

    easy10 min

    Use forEach to total a list of numbers.

  3. 3

    Use the index

    easy10 min

    Number each name starting at 1, separated by spaces.

  4. 4

    Count matching values

    easy10 min

    Use forEach to count how many numbers are above 10.

  5. 5

    Show forEach returns nothing

    medium10 min

    Store the result of forEach and show its type.

Find the bug(5)

  1. 1

    Fix the result of forEach being used

    easy8 min

    forEach returns nothing, so the doubled values were lost.

  2. 2

    Fix the total declared inside

    easy8 min

    Declaring the total inside the callback resets it every time.

  3. 3

    Fix the arguments in the wrong order

    easy8 min

    The value comes first and the index second, so the labels came out backwards.

  4. 4

    Fix the numbering starting at zero

    easy8 min

    The list should be numbered from 1.

  5. 5

    Fix the early exit that never happens

    easy8 min

    return inside forEach only skips one turn, so the count keeps rising.

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