Mastering Immutable.js

Filtering list intersections

Let's implement another intersect() function that uses method chaining to filter out the intersecting list values:

const intersection = (...lists) =>  List()    .concat(...lists)    .countBy(v => v)    .toSeq()    .filter(v => v === lists.length)    .keySeq();

This is much easier to read. Let's break down what's happening here:

• concat(...lists): This joins all list arguments together, resulting in one big list
• countBy(v => v): This creates a map where the keys are the unique list values, and the map values are the number or occurrences in the list
• toSeq(): This enables lazy evaluation from this point forward
• filter(v => v === lists.length): This finds intersecting values by checking if its count is the same as the number of ...