bhabig/javascript-pure-functions-lab-learn-experts-testing-batch

JavaScript Pure Functions Lab

Overview

In this lab, you'll write non-side-effecting functions and you'll chain updates without mutating global state.

Late to the party

Let's pretend we've been living under a rock for the last couple of months, and haven't been keeping up with the latest TV shows. Our friend tells us that the latest season of Game of Thrones has been released for quite some time now. Why were we not informed of this sooner?! It's time for some good 'ol binge watching!

In the index.js file, there is a list of episodes, as well as the finale episode in a separate variable. Your tasks for this lab are as follows:

1. Create a addToPlaylist() function that takes a playlist and an episode as arguments, and returns a new array with the episode appended to the playlist. This function must not modify the original array! This function is used to create a playlist that also contains the finale episode.

2. Create a removeFromPlaylist() function that takes a playlist and an episode, and returns a new array with that episode removed from the array. This function must also not modify the original array.

3. Create a getNextEpisodeInPlaylist() function that returns the first episode in a playlist.

4. Finally, to tie it all together, create a function called bingeWatch() that takes a playlist as its only argument. This function recursively calls itself: as long as there is a next episode, we watch it (by removing it from the playlist), and then we continue our binge watching session. If there are no more episodes in the playlist, we return the string 'Please let there be more!'. Sadly for us, there aren't any more episodes in this season. Such a long wait.

NOTE: Unfortunately, due to JavaScript quirks, you'll need to write bingeWatch() with function syntax for the tests to pass:

function bingeWatch() { ... }

In the "real world," using an arrow function would be fine —

const bingeWatch = () => { ... }

— but it won't work here.

Resources

• Eloquent JavaScript: Functions