Math.random() 如何在 javascript 中工作? [英] How does Math.random() work in javascript?

问题描述

我最近想出了如何通过 google 获取随机数，这让我开始思考 Math.random() 是如何工作的.所以我在这里我无法弄清楚他们是如何做 Math.random() 的，除非他们使用了一个类似的时间，有人知道 JavaScript 的 Math.random() 是如何工作的或等效的吗?

I recently figured out how to get a random number via google, and it got me thinking how does Math.random() work. So here I am I can not figure out how they did Math.random() unless they used a time like thing does anyone know how JavaScript's Math.random() works or an equivalent?

推荐答案

Math.random() 返回一个带正号的 Number 值，大于或等于 0 但小于 1，随机或伪随机选择，近似均匀使用依赖于实现的算法或策略在该范围内分布.

Math.random() returns a Number value with a positive sign, greater than or equal to 0 but less than 1, chosen randomly or pseudo randomly with approximately uniform distribution over that range, using an implementation-dependent algorithm or strategy.

这是 V8 的实现:

uint32_t V8::Random() {

    // Random number generator using George Marsaglia's MWC algorithm.
    static uint32_t hi = 0;
    static uint32_t lo = 0;

    // Initialize seed using the system random(). If one of the seeds
    // should ever become zero again, or if random() returns zero, we
    // avoid getting stuck with zero bits in hi or lo by reinitializing
    // them on demand.
    if (hi == 0) hi = random();
    if (lo == 0) lo = random();

    // Mix the bits.
    hi = 36969 * (hi & 0xFFFF) + (hi >> 16);
    lo = 18273 * (lo & 0xFFFF) + (lo >> 16);
    return (hi << 16) + (lo & 0xFFFF);
}

来源:http://dl.packetstormsecurity.net/papers/general/Google_Chrome_3.0_Beta_Math.random_vulnerability.pdf

以下是 StackOverflow 上的几个相关线程:

Here are a couple of related threads on StackOverflow:

• 为什么 Google Chrome 的 Math.random数字生成器不是*那个*随机的吗?
• JavaScript 的 Math.random 有多随机?

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