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JavaScript Object freeze — exercises and bug fixes

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

    Freeze an object

    easy10 min

    Freeze a settings object, try to change it, and show the value stayed put.

  2. 2

    Check whether it is frozen

    easy10 min

    Show whether a frozen object reports as frozen.

  3. 3

    Show const is not enough

    easy10 min

    Change a property on a const object and show the new value.

  4. 4

    Seal an object

    easy10 min

    Seal an object, change a value, try to add one, and show how many properties there are.

  5. 5

    Show freezing is shallow

    medium10 min

    Freeze an object with a nested object, change the nested value, and show it.

Find the bug(5)

  1. 1

    Fix the object that was not frozen

    easy8 min

    const alone does not stop the property being changed.

  2. 2

    Fix the freeze result thrown away

    easy8 min

    freeze returns the object, and the returned value was ignored.

  3. 3

    Fix seal used where freeze is needed

    easy8 min

    A sealed object still allows its values to change.

  4. 4

    Fix freeze used where seal is needed

    easy8 min

    The value should still be editable, but new properties must be refused.

  5. 5

    Fix the nested value left unprotected

    easy8 min

    Freezing only locks the top level, so the nested host still changed.

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