记忆 - 阶乘函数

var memoizer = function(memo, fundamental) {
        var shell = function(n) {
                var result = memo[n];
                if (typeof result !== 'number') {
                    result = fundamental(shell, n);
                    memo[n] = result;
                }
                return result;
            };
        return shell;
    };

//阶乘函数
var factorial = memoizer([1, 1], function(shell, n) {
    return n * shell(n - 1);
});
for (var i = 0; i <= 10; i += 1) {
    document.writeln('//' + i + ': ' + factorial(i) + '<br/>');
}