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JavaScript Keywords — exercises and bug fixes

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

    Use the const keyword

    easy10 min

    Declare a constant and display it.

  2. 2

    Use the typeof keyword

    easy10 min

    Report the type of true.

  3. 3

    Use the return keyword

    easy10 min

    Return a value from a function and show it.

  4. 4

    Use the new keyword

    easy10 min

    Create a Date and confirm it worked.

  5. 5

    Use the this keyword

    medium10 min

    Read a property through this inside a method.

Find the bug(5)

  1. 1

    Fix the reserved word used as a name

    easy8 min

    class is a reserved keyword and cannot be a variable name.

  2. 2

    Fix the missing return

    easy8 min

    The function computes a value but never returns it.

  3. 3

    Fix the missing new keyword

    easy8 min

    Date without new returns a string, not a Date object.

  4. 4

    Fix the wrong typeof target

    easy8 min

    This reports the type of a string, not a boolean.

  5. 5

    Fix this inside an arrow function

    easy8 min

    An arrow method has no own this, so the lookup fails.

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