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JavaScript Primitives and References — exercises and bug fixes

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

    Copy a primitive

    easy10 min

    Copy a number, change the copy, and report the original.

  2. 2

    Share an object

    easy10 min

    Assign an object to a second name, change it, and report the first.

  3. 3

    Copy an object properly

    easy10 min

    Spread the object so the original is left alone.

  4. 4

    Copy an array

    easy10 min

    Spread an array, push to the copy, and report both lengths.

  5. 5

    Change an object in a function

    medium10 min

    Show that a property changed inside a function is visible outside.

Find the bug(5)

  1. 1

    Fix the object shared instead of copied

    easy8 min

    A plain assignment shares the object.

  2. 2

    Fix the array shared

    easy8 min

    Pushing to the second name changes the first array too.

  3. 3

    Fix the objects compared by contents

    easy8 min

    Two separate objects are never equal, however alike.

  4. 4

    Fix the reassignment inside a function

    easy8 min

    Replacing the whole object inside a function is not visible outside.

  5. 5

    Fix the nested object still shared

    easy8 min

    Spreading copies only the top level, so the inner object is shared.

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