Memoize High Order Function that can handle multiple and nested arguments

memoize-multiple-arguments.js

function equals(a, b) {
    if (a === b) return true;
    if (a instanceof Date && b instanceof Date) return a.getTime() === b.getTime();
    if (!a || !b || (typeof a !== 'object' && typeof b !== 'object')) return a === b;
    if (a.prototype !== b.prototype) return false;
    const keys = Object.keys(a);
    if (keys.length !== Object.keys(b).length) return false;
    return keys.every(k => equals(a[k], b[k]));
};


function memoizer(fun) {
    var pastArgs = new Set();

    function getArgsKey(args = []) {
        for (const k of pastArgs.keys()) {
            if (equals(args, k)) return k;
        }

        pastArgs.add(args);
        return args;
    }
    
    let cache = new Map();
    return function (...args) {
        const argsKey = getArgsKey(args);
        if (cache.get(argsKey) !== undefined) {
            return cache.get(argsKey);
        } else {
            const result = fun(...args)
            cache.set(argsKey, result);
            return result
        }
    }
}

var add = (x, y) => console.log(`adding ${x} and ${y}`) || x + y;
var cachedAdd = memoizer(add);

console.log(cachedAdd(1, 2))
console.log(cachedAdd(1, 2))

var getProp = (o, k) => console.log(`computing getProp with ${k}`) || o[k];
var cachedGetProp = memoizer(getProp);

console.log(cachedGetProp({ name: 'Felix' }, 'name'))
console.log(cachedGetProp({ name: 'Felix' }, 'name'))