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seedablerandompublic
Seedable pseudorandom number generator
Usage
var random = require('seedablerandom');
random.seed(123);
console.log(random());
As a Math.random
replacement
Math.random = require('seedablerandom');
Math.random.seed(12345);

Works as a dropin for
Math.random

Relatively fast (about 2.5 times slower than
Math.random
on my machine) 
Seeds itself from the clock by default

Tries to be pretty random

Well tested (TODO come up with some PRNG torture tests)
TODO
Possibility to switch the generator (linearfeedback shift register, Mersenne twister, digits of Math.sin(), etc. based on your needs)
A word of warning
Current implementation just calls Math.sin() with the seed. It's likely that it's not quite that random (for example, the distribution could be biased towards numbers near 1.0). Some more tests are needed.