Flatten one level — practice exercise

What you'll be asked to do

1. 1.Flatten one levelexercise · easy · 10 min

   Flatten a nested array and join the result with commas.

   Passes when: #out should show 1,2,3,4.

2. 2.Flatten two levelsexercise · easy · 10 min · practice plan

   Flatten an array nested two deep and show the length.

   Passes when: #out should show 4.

3. 3.Flatten completelyexercise · easy · 10 min · practice plan

   Use Infinity to flatten however deep the nesting goes.

   Passes when: #out should show 1,2,3,4.

4. 4.Split into wordsexercise · easy · 10 min · practice plan

   Use flatMap to split each sentence into words and join with commas.

   Passes when: #out should show a,b,c,d.

5. 5.Merge groups of namesexercise · medium · 10 min · practice plan

   Flatten an array of groups and show the total number of people.

   Passes when: #out should show 4.

6. 6.Fix the default depthbug fix · easy · 8 min

   One level is not enough for an array nested two deep.

   Passes when: #out should show 4.

7. 7.Fix map used instead of flatMapbug fix · easy · 8 min · practice plan

   map leaves each result nested inside its own array.

   Passes when: #out should show a,b,c,d.

8. 8.Fix the result of flat being ignoredbug fix · easy · 8 min · practice plan

   flat returns a new array; it does not change the original.

   Passes when: #out should show 1,2,3,4.

9. 9.Fix the fixed depth on unknown nestingbug fix · easy · 8 min · practice plan

   The nesting is deeper than the depth given.

   Passes when: #out should show 1,2,3,4.

10. 10.Fix concat used on nested groupsbug fix · easy · 8 min · practice plan

    The groups need flattening into one list of people.

    Passes when: #out should show 4.

Between them these tasks cover flat, flatMap and Nested arrays.

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