JS-PRNG v0.2.3

JS-PRNG is a small pseudorandom number generator written in JavaScript that can be used to generate any number of seemingly random numbers based on the given initial 32-bit seed value and other inputs. Both numbers and strings are supported as valid seed values. It uses XOR operations as well as bit-shift operations to achieve pseudorandomness. The distribution of the random numbers is very uniform.

Demonstrations of distribution:

• nextBetween(): https://tom-granig.github.io/JS-PRNG/examples/Noise-Patterns.html
  
• getNoise1D(x): https://tom-granig.github.io/JS-PRNG/examples/Noise-Patterns-getNoise1D.html
  
• getNoise2D(x, y): https://tom-granig.github.io/JS-PRNG/examples/Noise-Patterns-getNoise2D.html
  

NOTE: This generator is not intended to be cryptographically secure and should not be used for any cryptographic or other purposes where security is vital. Consider using the SubtleCrypto API instead.

How To Use

Generate numbers in the range [0, 1)

The next() function returns the next random floating point value between 0, inclusive and 1, exclusive.

// creates a new PRNG object and initializes it with the seed 324792302:
const generator = new PRNG(324792302); 
console.log(generator.next()); // prints out "0.31638280814513564"
console.log(generator.next()); // prints out "0.934757471550256"

Generate intergers in the range [a, b]

The nextBetween(a, b) function returns the next random integer between and including a and b.

// creates a new PRNG object and initializes it with the seed 324792302:
const generator = new PRNG(324792302);
console.log(generator.nextBetween(1, 6)); // prints out "2"
console.log(generator.nextBetween(1, 6)); // prints out "6"

Using a string as a seed

Strings can be used as seeds, with character values above 255 (end of ASCII range) wrapping over.

// creates a new PRNG object and initializes it with the seed "hello world!":
const generator = new PRNG('hello world!');
console.log(generator.next()); // prints out "0.6686770371161401"
console.log(generator.next()); // prints out "0.3518891027197242"

Changing the seed

The seed can be changed with the seed(seedValue) function without having to create a new PRNG object.

// creates a new PRNG object and initializes it with the seed "hello world!":
const generator = new PRNG('hello world!');
console.log(generator.next()); // prints out "0.6686770371161401"
console.log(generator.next()); // prints out "0.3518891027197242"

generator.seed(324792302); // updates the generator's seed to 324792302
console.log(generator.next()); // prints out "0.31638280814513564"
console.log(generator.next()); // prints out "0.934757471550256"

Resetting the generator

The generator can be reset with reset() to the state it was in before any numbers were generated after setting the seed or creating the object.

// creates a new PRNG object and initializes it with the seed "hello world!":
const generator = new PRNG('hello world!');
console.log(generator.next()); // prints out "0.6686770371161401"
console.log(generator.next()); // prints out "0.3518891027197242"

generator.reset(); // resets the generator's seed and state to "hello world!"
console.log(generator.next()); // prints out "0.6686770371161401"
console.log(generator.next()); // prints out "0.3518891027197242"

generator.seed(324792302); // updates the generator's seed to 324792302
console.log(generator.next()); // prints out "0.31638280814513564"
console.log(generator.next()); // prints out "0.934757471550256"

generator.reset(); // resets the generator's seed and state to 324792302
console.log(generator.next()); // prints out "0.31638280814513564"
console.log(generator.next()); // prints out "0.934757471550256"

Getting 1D and 2D noise values in the range [0, 1)

One dimensional and two dimensional based noise values can be obtained with the functions getNoise1D(x) and getNoise2D(x, y), where if the same x and y values are supplied, and the initial seed value is the same, the same noise value will always be generated. Using next() and nextBetween() will not affect the values these functions produce.
Note: This does not return smoothed noise, you could interpolate it or use perlin or simplex noise.
Example: https://tom-granig.github.io/JS-PRNG/examples/Noise-Patterns-getNoise2D.html

1D noise

One dimensional noise bases its "random" value on a single input, x, as well as the seed value.

// creates a new PRNG object and initializes it with the seed "a seed":
const generator = new PRNG('a seed');
// the same value is produced with the same input and seed:
console.log(generator.getNoise1D(12)); // prints out "0.3391361958347261"
console.log(generator.getNoise1D(12)); // prints out "0.3391361958347261"

// a different value is produced with a different input:
console.log(generator.getNoise1D(13)); // prints out "0.40557587472721934"
console.log(generator.getNoise1D(12)); // prints out "0.3391361958347261"

generator.seed('a new seed'); // updates the generator's seed to "a new seed"
// although the input, 13, is the same, due to the different seed value, a different value is generated:
console.log(generator.getNoise1D(13)); // prints out "0.6760188862681389"

2D noise

Two dimensional noise bases its "random" value on two inputs, x and y, as well as the seed value.

// creates a new PRNG object and initializes it with the seed "a seed":
const generator = new PRNG('a seed');
// the same value is produced with the same inputs and seed:
console.log(generator.getNoise2D(100, 200)); // prints out "0.6134800035506487"
console.log(generator.getNoise2D(100, 200)); // prints out "0.6134800035506487"

// a different value is produced with different inputs:
console.log(generator.getNoise2D(101, 200)); // prints out "0.14556610770523548"
console.log(generator.getNoise2D(100, 200)); // prints out "0.6134800035506487"

generator.seed('a new seed'); // updates the generator's seed to "a new seed"
// although the inputs, 101 and 200, are the same, due to the different seed value, a different value is generated:
console.log(generator.getNoise2D(101, 200)); // prints out "0.4730283385142684"