Transform with map — practice exercise

What you'll be asked to do

1. 1.Transform with mapexercise · easy · 10 min

   Add 20 percent to each price and join the results with commas.

   Passes when: #out should show 120,240.

2. 2.Keep some with filterexercise · easy · 10 min · practice plan

   Keep only numbers above 4 and join them with commas.

   Passes when: #out should show 8,12,5.

3. 3.Total with reduceexercise · easy · 10 min · practice plan

   Add 1, 2, 3 and 4 together using reduce.

   Passes when: #out should show 10.

4. 4.Return a functionexercise · easy · 10 min · practice plan

   Write a function that builds a multiplier, then triple 15.

   Passes when: #out should show 45.

5. 5.Chain them togetherexercise · medium · 10 min · practice plan

   Keep the even numbers from 1 to 6, multiply each by 10, and add them up.

   Passes when: #out should show 120.

6. 6.Fix forEach used instead of mapbug fix · easy · 8 min

   forEach returns nothing, so there is no new array.

   Passes when: #out should show 120,240.

7. 7.Fix the filter that returns nothingbug fix · easy · 8 min · practice plan

   The callback has braces but no return, so nothing is kept.

   Passes when: #out should show 8,12,5.

8. 8.Fix the missing starting valuebug fix · easy · 8 min · practice plan

   Without a starting value the first item is used as the total.

   Passes when: #out should show 20.

9. 9.Fix the function called instead of returnedbug fix · easy · 8 min · practice plan

   The outer function returns a number, not a function.

   Passes when: #out should show 45.

10. 10.Fix the wrong chain orderbug fix · easy · 8 min · practice plan

    Multiplying before filtering changes which numbers are kept.

    Passes when: #out should show 120.

Between them these tasks cover map, filter, reduce, Returning functions and Chaining.

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