Memo function

gistfile1.js

const memo = (function () {
    const cache = new Map()
    return function (fn, ctx = null, ...params) {
        if (cache.has([fn, params, ctx].toString())) {
            return cache.get([fn, params, ctx].toString())
        } else {
            const res = fn.call(ctx, ...params);
            cache.set([fn, params, ctx].toString(), res);
            return res;
        }
    }
})()