Is there something like mulitiSet in JavaScript?

Question

I know that JavaScript now has sets, but I wonder if there is something to realize the function of multiSet, or if there is some framework that has the functions of multiset which I really need a lot.

Or I have to code it by myself to do the research of Red-Black Tree?

@jfriend00 Exactly this search brought me here, following your instructions would create an infinite loop :-) — Konrad Höffner, Oct 07 '17 at 17:10
You don't need a redblack tree, what you could probably use is a sorted list, binary search, and a operator for merging sorted lists. — Justin Meiners, Jun 21 '21 at 22:47

score 3 · Answer 1 · answered Feb 12 '18 at 19:10

3

There are no built-in multiset structure, but there are some libraries that have such:

mnemonist → MultiSet
TSTL → TreeMultiSet

Feel free to add your favorite library in this question.

answered Feb 12 '18 at 19:10

diralik

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score 2 · Answer 2 · answered Jul 06 '21 at 17:47

You can build your own multiset using the Builtin map type and numerical values:

class Multiset {
    _backing = new Map();
    add(value) {
        if (this._backing.has(value)) {
            this._backing.set(value, 1 + this._backing.get(value));
        } else {
            this._backing.set(value, 1);
        }
    }

    delete(value) {
        if (this._backing.get(value) > 0) {
            this._backing.set(value, this._backing.get(value) - 1);
        } else {
            //do nothing
        }
    }

    get(value) {
        if (this._backing.get(value) > 0) {
            return this._backing.get(value);
        } else {
            return 0;
        }
    }
}

score 1 · Answer 3 · answered Oct 27 '22 at 10:53

1

This is an old question, but it came in at the top of my search. I've ended up using lodash (similar to underscore): For example,

_.countBy([1, 2, 1, 4, 4, 1])

gives the result

{ '1': 3, '2': 1, '4': 2 }

answered Oct 27 '22 at 10:53

whistling_marmot

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3
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Is there something like mulitiSet in JavaScript?

3 Answers3

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