September 2022
Intermediate to advanced
585 pages
8h 17m
Chinese
Content preview from JavaScript 经典实例：第三版
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数字
｜
79
3.2
生成密码学上安全的随机数
3.2.1
问题
你想生成不能轻易逆向工程（猜出）的随机数。
3.2.2
方案
使用
window.crypto
属性获取
Crypto
对象的实例，使用
Crypto.getRandom-
Values()
方法生成随机值。这比使用
Math.random()
生成的随机值具有更高的熵（换
句话说就是，更难重复或预测。详见
3.2.3
节）。
Crypto.getRandomValues()
方法的用法与
Math.random()
方法不同。
getRandom-
Values()
不生成一个
0
～
1
之间的浮点数，而是使用随机的整数填充一个数组。这
些整数可以是
8
位、
16
位或
32
位，也可以带符号或不带符号（带符号的数据类型
可以为负数或正数，而不带符号的数字只能是正数）。
有一种普遍接受的方法可以把
getRandomValues()
的
输出转换成一个
0
～
1
之间的
小数，即拿随机值除以相应数据类型最大的数。
const
randomBuffer =
new
Uint32Array(1);
window.crypto.getRandomValues(randomBuffer);
const
randomFraction = randomBuffer[0] / (0xffffffff + 1);
现在，可以像
Math.random()
方法返回的随机数一样处理
randomFraction
了。例如，
可以把它转换为指定范围内的一个随机整数，详见
3.1
节。
//
使用随机小数生成一个
1
到
6
之间的随机整数
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.