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JavaScript DOM Collections — exercises and bug fixes

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

    Count the matches

    easy10 min

    Report how many paragraphs are on the page.

  2. 2

    Loop with forEach

    easy10 min

    Join the text of every row using forEach.

  3. 3

    Turn a NodeList into an array

    easy10 min

    Use Array.from with map to join the row texts with dashes.

  4. 4

    Filter elements

    easy10 min

    Count how many rows have the class on.

  5. 5

    Show a NodeList is not an array

    medium10 min

    Report whether a NodeList is a real array.

Find the bug(5)

  1. 1

    Fix map called on a NodeList

    easy8 min

    A NodeList has forEach but not map.

  2. 2

    Fix the live collection removed in a loop

    easy8 min

    Removing from a live collection while looping skips elements.

  3. 3

    Fix the stale static list

    easy8 min

    A NodeList does not update when elements are added.

  4. 4

    Fix the collection used as one element

    easy8 min

    querySelectorAll returns a list, so textContent must be read per element.

  5. 5

    Fix the index used on a single element

    easy8 min

    querySelector returns one element, which cannot be indexed.

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