const fibonacci = (n) => {

    if (n <= 1) return 1;

    return fibonacci(n - 1) + fibonacci(n - 2);

};

​

fibonacci(20);

​

const memoize = function(func) {

    var stringifyJson = JSON.stringify,

        cache = {};

​

    var cachedfun = function() {

        var hash = stringifyJson(arguments);

        return hash in cache ? cache[hash] : (cache[hash] = func.apply(this, arguments));

    };

​

    cachedfun.__cache = function() {

        cache.remove ||

            (cache.remove = function() {

                var hash = stringifyJson(arguments);

                return delete cache[hash];

            });

        return cache;

    }.call(this);

​

    return cachedfun;

};

​

const fibonacci = memoize((n) => {

    if (n <= 1) return 1;

    return fibonacci(n - 1) + fibonacci(n - 2);

});

​

fibonacci(20);

​

const memoize = function(func) {

    const cache= {}

    return (...args) => {

      const n = args[0]

      if (n in cache) {

        return cache[n];

      } else {

        const result = func(n)

        cache[n] = result

        return result

      }

    }

};

​

const fibonacci = memoize((n) => {

    if (n <= 1) return 1;

    return fibonacci(n - 1) + fibonacci(n - 2);

});

​

fibonacci(20);

​