Creates a Linear Congruential Generator for generating random numbers. The random numbers are predictable/reproducable, which is useful for (unit) testing purposes.

npm install lcg-random --save

A call to the exported function returns a function that generates a random number on every call:

var lcgRandom = require("lcg-random");

// Outputs 0.000007826369259425611 0.13153778814316625 0.7556053221950332
var rand1 = lcgRandom();
console.log(rand1(), rand1(), rand1());

// Also outputs 0.000007826369259425611 0.13153778814316625 0.7556053221950332
var rand2 = lcgRandom();
console.log(rand2(), rand2(), rand2());

Returns a function that returns a random number between 0 and 1 every time it is called.

The function used is

X_n+1 = (multiplier * X_n + increment) % modulus

Every component of the function can be customized by setting it in the options argument. The default values are the ones from Park and Miller's MINSTD.

• options.seed - number (0 ≤ options.seed < options.modulus)
  Seed (start value) for the generator.
  Default: 1

• options.modulus - modulus (0 < options.modulus)
  Modulus for the generator.
  Default: 2³¹-1

• options.multiplier - modulus (0 < options.multiplier < options.modulus)
  Multiplier for the generator.
  Default: 7⁵

• options.increment - modulus (0 ≤ options.increment < options.modulus)
  Increment for the generator.
  Default: 0

• Allow increment of 0 (enabling Lehmer RNGs) (#1)
• Use MINSTD as default values (#1)
• Change default seed to 1 (to enable MINSTD)
• Add bounds checks

• Fix index in package.json

• Initial version