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JavaScript Math.random — exercises and bug fixes

5 hands-on exercises and 5 find-the-bug challenges for the JavaScript Math.random 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

    Check the basic range

    easy10 min

    Report that a random value falls from zero up to one.

  2. 2

    Make a whole number

    easy10 min

    Produce a whole number from zero to nine and check it.

  3. 3

    Roll a dice

    easy10 min

    Produce a value from one to six and check it.

  4. 4

    Use any range

    easy10 min

    Write a function giving a value between ten and twenty inclusive.

  5. 5

    Pick from an array

    medium10 min

    Choose a random colour and confirm it came from the list.

Find the bug(5)

  1. 1

    Fix the missing floor

    easy8 min

    Without floor the dice value is a decimal.

  2. 2

    Fix round used instead of floor

    easy8 min

    Rounding can reach ten, which is outside the wanted range.

  3. 3

    Fix the range missing its top value

    easy8 min

    Without the plus one the maximum can never appear.

  4. 4

    Fix the index off the end

    easy8 min

    Multiplying by the length gives a valid index only after flooring.

  5. 5

    Fix the minimum never added

    easy8 min

    Without adding the minimum the range starts at zero.

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