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JavaScript String trim — exercises and bug fixes

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

    Trim the ends

    easy10 min

    Remove the spaces around the name.

  2. 2

    Detect an empty field

    easy10 min

    Report that a field of spaces is really empty.

  3. 3

    Pad a number

    easy10 min

    Add a leading zero to the minutes.

  4. 4

    Build a clock time

    easy10 min

    Pad both parts to make a proper time.

  5. 5

    Mask a card number

    medium10 min

    Show only the last four digits.

Find the bug(5)

  1. 1

    Fix the untrimmed check

    easy8 min

    A field of spaces is being treated as filled in.

  2. 2

    Fix the trim result discarded

    easy8 min

    trim returns a new string and does not change the original.

  3. 3

    Fix padEnd used for a leading zero

    easy8 min

    The zero belongs at the front.

  4. 4

    Fix the number not converted

    easy8 min

    padStart is a string method, so the number needs converting first.

  5. 5

    Fix the target length too short

    easy8 min

    The mask needs to reach twelve characters.

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