functionalscript/types/map/module.f.js

FunctionalScript is a purely functional subset of JavaScript

const concat = (x, y) => ({
    *[Symbol.iterator]() {
        yield* x;
        yield* y;
    }
});
const filter = (i, p) => ({
    *[Symbol.iterator]() {
        for (const x of i) {
            if (p(x)) {
                yield x;
            }
        }
    }
});
export const mapSet = (map, k, v) => new Map(concat(map, [[k, v]]));
export const mapDelete = (map, k) => new Map(filter(map, ([xk]) => xk !== k));