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JavaScript Map — exercises and bug fixes

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

    Store and read a value

    easy10 min

    Put a score in a Map and read it back.

  2. 2

    Count the entries

    easy10 min

    Report how many entries the Map holds.

  3. 3

    Use a number as a key

    easy10 min

    Store a value under a numeric key and read it back.

  4. 4

    Remove an entry

    easy10 min

    Delete an entry and report whether it is still there.

  5. 5

    Build from an array of pairs

    medium10 min

    Create a Map from pairs and read one value.

Find the bug(5)

  1. 1

    Fix the object used for a numeric key

    easy8 min

    An object turns every key into a string.

  2. 2

    Fix size called as a method

    easy8 min

    size is a property, not a method.

  3. 3

    Fix bracket access on a Map

    easy8 min

    A Map is read with get, not with square brackets.

  4. 4

    Fix the flat array passed in

    easy8 min

    A Map is built from pairs, not a flat list.

  5. 5

    Fix delete used with the value

    easy8 min

    delete takes the key, not the value.

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