Use JSON.stringify for storing in Sets

Set can store different kinds of element, but specifically for storing Arrays, you will have to use JSON.stringify() to avoid duplication.

without stringify:

let set = new Set();
set.add([1]);
set.add([1]);

set.size; // => 2

with stringify:

set.add(JSON.stringify([1]));
set.add(JSON.stringify([1]));

set.size; // => 1

Also, whenever you want to pull the data back as Arrays, use JSON.parse with Array.prototype.map()

[...set] //=> '[1]'
[...set].map(JSON.parse) //=> [1]