nodejs javascript 实现随机数种子的几种方法

最简单的方法

http://stackoverflow.com/questions/521295/javascript-random-seeds

1. 用 Math.sin

var seed = 1;function random() {    var x = Math.sin(seed++) * 10000;    return x - Math.floor(x);}

简单封装下

Math.seed = function(s) {    return function() {        s = Math.sin(s) * 10000; return s - Math.floor(s);    };};// usage:var random1 = Math.seed(42);var random2 = Math.seed(random1());Math.random = Math.seed(random2());

2.这个稍复杂.不过随机性比sin更好.

var m_w = 123456789;var m_z = 987654321;var mask = 0xffffffff;// Takes any integerfunction seed(i) {    m_w = i;}// Returns number between 0 (inclusive) and 1.0 (exclusive),// just like Math.random().function random(){    m_z = (36969 * (m_z & 65535) + (m_z >> 16)) & mask;    m_w = (18000 * (m_w & 65535) + (m_w >> 16)) & mask;    var result = ((m_z << 16) + m_w) & mask;    result /= 4294967296;    return result + 0.5;}

封装下

Math.seed = function(s) {    var m_w  = s;    var m_z  = 987654321;    var mask = 0xffffffff;    return function() {      m_z = (36969 * (m_z & 65535) + (m_z >> 16)) & mask;      m_w = (18000 * (m_w & 65535) + (m_w >> 16)) & mask;      var result = ((m_z << 16) + m_w) & mask;      result /= 4294967296;      return result + 0.5;    }}//usagevar myRandomFunction = Math.seed(1234);var randomNumber = myRandomFunction();

正统的实现

https://github.com/davidbau/seedrandom

https://github.com/davidbau/seedrandom/blob/released/seedrandom.js

Script tag usage

<script src="//cdnjs.cloudflare.com/ajax/libs/seedrandom/2.4.0/seedrandom.min.js">
</script>

// Sets Math.random to a PRNG initialized using the given explicit seed.Math.seedrandom('hello.');console.log(Math.random());          // Always 0.9282578795792454console.log(Math.random());          // Always 0.3752569768646784// Sets Math.random to an ARC4-based PRNG that is autoseeded using the// current time, dom state, and other accumulated local entropy.// The generated seed string is returned.Math.seedrandom();console.log(Math.random());          // Reasonably unpredictable.// Seeds using the given explicit seed mixed with accumulated entropy.Math.seedrandom('added entropy.', { entropy: true });console.log(Math.random());          // As unpredictable as added entropy.// Use "new" to create a local prng without altering Math.random.var myrng = new Math.seedrandom('hello.');console.log(myrng());                // Always 0.9282578795792454// Use "quick" to get only 32 bits of randomness in a float.console.log(myrng.quick());          // Always 0.3752569768112153// Use "int32" to get a 32 bit (signed) integerconsole.log(myrng.int32());          // Always 986220731

Node.js usage

npm install seedrandom

// Local PRNG: does not affect Math.random.var seedrandom = require('seedrandom');var rng = seedrandom('hello.');console.log(rng());                  // Always 0.9282578795792454// Global PRNG: set Math.random.seedrandom('hello.', { global: true });console.log(Math.random());          // Always 0.9282578795792454// Autoseeded ARC4-based PRNG.rng = seedrandom();console.log(rng());                  // Reasonably unpredictable.// Mixing accumulated entropy.rng = seedrandom('added entropy.', { entropy: true });console.log(rng());                  // As unpredictable as added entropy.// Using alternate algorithms, as listed above.var rng2 = seedrandom.xor4096('hello.')console.log(rng2());