Choice.js

A random library for JavaScript

This is a utility library with several Random functions for javascript. It was originally developed to be used in "natural" code, for physics, generated drawings and such. See Nature of Code

Reference

All functions are namespaced under Choice, so randint(0, 5) is actually Choice.randint(0, 5)

• randint(min, max)
• choice(array)
• shuffle(array)
• rand()
• sample(array)
• gaussian(mean, standardDeviation)
• chance(percentage, [choices])
• probabilities(probabilities, outcomes)
• setSeed(seed)

Documentation

randint

randint(min, max)

Takes two integers, returns an integer equal to or larger than min, but smaller than max

min >= n < max

/**
 * Example outputs:
 * 0, 152, 839, 1499
 * but not 1500
 */
randint(0, 1500);

choice

choice(array)

Takes an array and returns a random element from the array

/**
 * Example outputs:
 * 1
 * 3
 * 4
 */
choice([1, 2, 3, 4, 5]);

// choice can take all kinds of types
choice(["a", function () {}, [1, 2, 3], 55]);

shuffle

shuffle(array)

Takes an array and returns an array with the elements shuffled around

shuffle([1, 2, 3, 4, 5]) -> ex output: [1, 3, 4, 5, 2]
shuffle(["a", "b", "c", "d"]) -> ex output: ["b", "d", "c", "a"]
Note that there's a chance that the array stays the same

rand

rand()

returns a number between 0.0 and 1.0, 1.0 not included. This is the exact same as calling Math.random

sample

sample(array, amount)

Takes an array and a number of elements, returns an array of randomly chosen elements from the original array.

/**
 * example outputs:
 * [8, 5, 1]
 * [1, 6, 2]
 */
sample([1, 2, 3, 4, 5, 6, 7, 8], 3); // take three random elements from the array

/**
 * example outputs:
 * [1, 1]
 * [1, 2]
 * [2, 1]
 * [2, 2]
 */
sample([1, 1, 2, 2], 2); // take two random elements from the array

gaussian

gaussian(mean, standardDeviation)

Takes a mean and a standard deviation. Returns a guassian random number. A Gaussian random number generator generates numbers mean - standardDeviation * 3 > n < mean + standardDeviation * 3 with n having a higher chance being close to the mean than far away. Note that gaussian distribution is also known as normal distribution

/**
 * This one generates numbers between 4 and 16
 * 9 //common
 * 9
 * 7
 * 12
 * 10 // common
 * 13
 * 4 // rare
 */
gaussian(10, 2);

/**
 * Generates numbers between -6 and 6
 * example outputs:
 * 0 // common
 * 2
 * -1
 * -1
 * -6 // rare
 */
gaussian(0, 2);

chance

chance(probability, [choices])

Takes a probability (percentage). Returns true or false based on that probability. Takes a second optional argument, an array of two items. If the chance is true, it returns the first item out of the array. Otherwise it will return the second.

chance(25); // has a 25% chance to return true
chance(70); // has a 70% chance to return true
chance(12, [1, 2]); // has a 12% chance to return 1 and an 88% chance to return 2

probabilities

probabilities(probabilities, outcomes)

Takes two arrays of equal length. The first one is a set of probabilities adding up to 100%. The second one is a list of items. Each probability corresponds to an item. Random.probabilities([2, 98], ["first item", "second item"]) has a 2% chance to return "first item" and a far higher, 98% chance to return "second item"

// in this case you could also use choice, since the probabilities are equal
probabilities([25, 25, 25, 25], ["green", "blue", "yellow", "white"]);

// this one has 15% chance to return "I get 500 gold"
// another 15% chance to return "I get 200 gold"
// and a far higher 70% to return "I get 50 gold"
probabilities([15, 15, 70], ["I get 500 gold", "I get 200 gold", "I get 50 gold"]);
probabilities([1, 2, 3], [1]) // fails, the arrays are not equal size and probabilites do not add up to 100

// remember, this is JavaScript, you can place whatever you want in the outcomes array, so functions will work just fine
probabilities([80, 20], [function () {
    console.log("I appear about 80% of the time! :)");
}, function () {
    console.log("I appear about 20% of the time! :(");
}])(); // these params () instantly call the chosen function

setSeed

setSeed(seed)

Normally, Choice uses Math.random() as its base random number generator. This is fine for most use-cases. If you need reproducible randomness however, you can use Choice.setSeed(seed) to get reproducible randomness.

Choice.setSeed(10);
var firstSeeded = Choice.rand(); // 0.07342434833517503

// Because seeded randomness is all about reproducible random numbers, we set the seed to 10 again, resetting the RNG
Choice.setSeed(10);

var secondSeeded = Choice.rand(); // 0.07342434833517503

// the numbers are equal, as expected.