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JavaScript Iterables — exercises and bug fixes

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

    Confirm an array is iterable

    easy10 min

    Report the type of an array's Symbol.iterator method.

  2. 2

    Loop over a Set

    easy10 min

    Use for of to collect values from a Set.

  3. 3

    Catch a non-iterable loop

    easy10 min

    Catch the error from looping over a plain object.

  4. 4

    Spread a string

    easy10 min

    Spread a string into an array of its characters.

  5. 5

    Tell iterable spread from object spread

    medium10 min

    Show both kinds of spread working on their own kind of value.

Find the bug(5)

  1. 1

    Fix for of used on a plain object

    easy8 min

    Plain objects are not iterable.

  2. 2

    Fix the spread of a plain object as a list

    easy8 min

    Spreading an object into an array position needs it to be iterable.

  3. 3

    Fix the Map assumed non-iterable

    easy8 min

    A Map is iterable, yielding key-value pairs.

  4. 4

    Fix the string spread miscounted

    easy8 min

    Spreading a string gives one entry per character, not per byte pair blindly assumed.

  5. 5

    Fix destructuring used on a non-iterable

    easy8 min

    Array destructuring needs an iterable on the right side.

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