Too much temporary data and inefficient operations #14
Description
Consider using the standard .values instead of the custom .toArray. Besides, I'd also suggest to use Set's methods as much as possible since it is implemented as a hashset, which is very efficient, instead of relying on Array's methods which usually take at least linear time.
For example, .intersection could be implemented along the following lines
intersection(s1, s2) {
s3 = new Set();
s1.forEach(value => {
if (s2.has(value)) {
s3.add(value);
}
});
return s3;
}