JavaScript中最快的因子函数是什么？ [英] What is the fastest factorial function in JavaScript?

问题描述

在JavaScript中寻找一个非常快速的 factorial 函数实现。有什么建议吗？

Looking for a really fast implementation of factorial function in JavaScript. Any suggests?

推荐答案

如果你正在使用自然数字，查找表是显而易见的方法。
要实时计算任何阶乘，您可以使用缓存加速它，从而节省您之前计算过的数字。类似于：

Lookup table is the obvious way to go, if you're working with natural numbers. To calculate any factorial in real-time, you can speed it with a cache, saving the numbers you've calculated before. Something like:

factorial = (function() {
    var cache = {},
        fn = function(n) {
            if (n === 0) {
                return 1;
            } else if (cache[n]) {
                return cache[n];
            }
            return cache[n] = n * fn(n -1);
        };
    return fn;
})();

您可以预先计算某些值，以便加快速度。

You can precalculate some values in order to speed it even more.

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