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JavaScript Regex Anchors — exercises and bug fixes

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

    Anchor both ends

    easy10 min

    Reject a value that merely contains four digits.

  2. 2

    Anchor the start

    easy10 min

    Check the address begins with https.

  3. 3

    Anchor the end

    easy10 min

    Check the file name ends with pdf.

  4. 4

    Use a word boundary

    easy10 min

    Check cat does not match inside concatenate.

  5. 5

    Count whole words

    medium10 min

    Count only the standalone occurrences of cat.

Find the bug(5)

  1. 1

    Fix the unanchored validation

    easy8 min

    Without anchors any text containing four digits passes.

  2. 2

    Fix the extension checked at the start

    easy8 min

    The extension is at the end of the name.

  3. 3

    Fix the missing end anchor

    easy8 min

    Without the end anchor a disguised file passes.

  4. 4

    Fix the missing word boundaries

    easy8 min

    Without boundaries the word matches inside a longer one.

  5. 5

    Fix the caret used inside brackets

    easy8 min

    Inside brackets a caret inverts the set rather than anchoring to the start.

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