为什么 Set.prototype.has() 比 Array.prototype.includes() 快得多？ 节点 v10

Question

I have two arrays of strings, both having a length of ~150000. I wanted to find shared elements between the two, so I used filter() on array1, and for each element checked if array2.includes[array1element]. this was taking around 1.5 mins to finish executing, however when I changed the arrays to sets, and used set2.has(set1element), it executed in <1s to filter. I spread the contents of set1 into an array, but searching is being done on set2 using Set.prototype.has().

I'm new to sets, I actually just discovered them because arrays were taking so long to search through and I was looking for alternatives. Can someone explain why there is such a significant time difference? I don't have much of a maths background so answers with less mathematical/algorithmic jargon are appreciated!

CODE: where wireBpath and wireApath are arrays of strings: runtime ~1.5mins

let intersections = wireBpath.filter(position => wireApath.includes(position));

where wireBpath is an array(spread from a set to use the filter() method), and wireApath is a set: runtime<1s

let intersections = wireBpath.filter(position => wireApath.has(position));```

Answer 1

That is because the time complexity is different for Set and Array

The methods used by Sets to search for items has a time complexity of just O(1) , but the methods an array uses to search for items has a linear time complexity of O(N) . In other words, the run-time increases at the same rate as the size of the data increases.

For more details you can see this article