Challenges

collectNames(ids) should resolve every name and report the count and the type of the first entry, so collectNames([1,2]) gives "2-string".

Async race condition

bookSeats(n) handles n concurrent booking requests for a single remaining seat and returns how many bookings succeeded. It should never exceed 1.

Async race condition

countLoads(n) makes n concurrent calls to a cached loader and returns how many times the expensive load actually ran. It should always be 1.

Async race condition

doubleLater(value) should resolve to double the value after a short delay, so doubleLater(4) gives 8.

Async race condition

getName(id) should resolve to the loaded user's name, so getName(1) gives "user1".

Async race condition

loadAll(ids) should load every id and return all the results as an array, so loadAll([1, 2, 3]) returns [10, 20, 30].

Async race condition

tallyVotes(votes) should add up every vote, so tallyVotes([1, 2, 3, 4]) returns 10.

Async race condition

safeDivide(a, b) should return a / b, or -1 when the division fails. safeDivide(10, 0) should return -1.

Async race condition

sumAsync(nums) should add up values fetched asynchronously, so sumAsync([1, 2, 3]) returns 6.

Async race condition

labelAll(items) should return the names in the same order they were passed in, regardless of how long each one takes.

Async race condition

sumDelayed(nums) should add up numbers that each arrive asynchronously, resolving to the total.

Async race condition

doubleAll(nums) should resolve to a list with every number doubled.

Async race condition

wordLengths(words) should resolve to a list of each word's length.

Async race condition

delayedDouble(n) should asynchronously resolve to n doubled, e.g. delayedDouble(5) eventually resolves to 10.

Async race condition