<!-- BEGIN COPY / PASTE -->
        function memoize(fn) {
            const cache = new Map();
            return function(...args) {
                const key = JSON.stringify(args);
                if (cache.has(key)) {
                    return cache.get(key);
                }
                const result = fn(...args);
                cache.set(key, result);
                return result;
            };
        }

        // Example usage
        const slowFunction = (num) => {
            console.log("Computing...");
            return num * 2;
        };

        const fastFunction = memoize(slowFunction);

        console.log(fastFunction(5)); // Computing... 10
        console.log(fastFunction(5)); // 10 (cached result)
        <!-- END COPY / PASTE -->