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JavaScript for in Loop — exercises and bug fixes

5 hands-on exercises and 5 find-the-bug challenges for the JavaScript for in Loop 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

    List the property names

    easy10 min

    Join the property names of the object with a dash.

  2. 2

    Count the properties

    easy10 min

    Count how many properties the object has.

  3. 3

    Add up the values

    easy10 min

    Add every value in the object together and show the total.

  4. 4

    Find a property by its value

    easy10 min

    Find which subject scored 25 and show its name.

  5. 5

    Join names and values

    medium10 min

    Build a string of every property as name=value, separated by commas.

Find the bug(5)

  1. 1

    Fix the value used as a name

    easy8 min

    The loop variable holds the property name, not the value.

  2. 2

    Fix the missing brackets

    easy8 min

    Adding the property name instead of the value gives the wrong total.

  3. 3

    Fix the dot used with a variable

    easy8 min

    scores.key looks for a property actually named "key".

  4. 4

    Fix the counter that counts letters

    easy8 min

    This counts the characters of each name instead of the properties.

  5. 5

    Fix the missing break

    easy8 min

    Without break the loop keeps going and reports the last match.

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