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JavaScript parseInt and parseFloat — exercises and bug fixes

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

    Read a number from text

    easy10 min

    Pull the number out of a CSS width.

  2. 2

    Keep the decimal part

    easy10 min

    Read the price from text that has words after it.

  3. 3

    Use a different base

    easy10 min

    Read a hexadecimal value.

  4. 4

    Handle unreadable text

    easy10 min

    Report a message when nothing can be read.

  5. 5

    Compare with Number

    medium10 min

    Show that Number rejects what parseInt accepts.

Find the bug(5)

  1. 1

    Fix Number used on a suffixed value

    easy8 min

    Number needs the whole string to be numeric.

  2. 2

    Fix parseInt losing the decimals

    easy8 min

    parseInt truncates, so the pence disappear.

  3. 3

    Fix the missing radix

    easy8 min

    Hexadecimal text needs a base of sixteen.

  4. 4

    Fix the unchecked NaN

    easy8 min

    A failed parse gives NaN, which must be checked with Number.isNaN.

  5. 5

    Fix parseInt used for validation

    easy8 min

    parseInt accepts junk after the number, so it is too lenient here.

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