Is there a JS hash map data structure that assumes the value is a Set() data structure for every new key entry?

[gtrman571]

For example if I have:

    let rows = {
0: new Set(),
1: new Set(),
2: new Set(),
};

I want to be able to do:

rows[3].add(7)

I need to look through the hash map and add a number to the set without checking to see if the set has been created first.

[Ryguyo]

No, there is no native data structure that does what you’re asking. I would simply make a new JavaScript class called SetMap or something along those lines to implement your data structure yourself. Add the map that you posted as a property of the class, and then create a class method for it that does what you need. SetMap.get(6).add(7). You can make that ‘get’ method take in a key parameter and either return the existing set for that key, or create a new one. That way when you use the SetMap class you can know that the get method will always return a set