List the property names — practice exercise

What you'll be asked to do

1. 1.List the property namesexercise · easy · 10 min

   Join the property names of the object with a dash.

   Passes when: #out should show name-age-city.

2. 2.Count the propertiesexercise · easy · 10 min · practice plan

   Count how many properties the object has.

   Passes when: #out should show 4.

3. 3.Add up the valuesexercise · easy · 10 min · practice plan

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

   Passes when: #out should show 90.

4. 4.Find a property by its valueexercise · easy · 10 min · practice plan

   Find which subject scored 25 and show its name.

   Passes when: #out should show science.

5. 5.Join names and valuesexercise · medium · 10 min · practice plan

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

   Passes when: #out should show a=1,b=2.

6. 6.Fix the value used as a namebug fix · easy · 8 min

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

   Passes when: #out should show name-age-city.

7. 7.Fix the missing bracketsbug fix · easy · 8 min · practice plan

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

   Passes when: #out should show 90.

8. 8.Fix the dot used with a variablebug fix · easy · 8 min · practice plan

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

   Passes when: #out should show 90.

9. 9.Fix the counter that counts lettersbug fix · easy · 8 min · practice plan

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

   Passes when: #out should show 4.

10. 10.Fix the missing breakbug fix · easy · 8 min · practice plan

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

    Passes when: #out should show the first match, maths.

Between them these tasks cover for in, Object properties and Reading values by key.

Looking for a different chapter? See every practice set, or switch to the interview theory questions.