Weighted-Randomly-Select

This package lets you easily perform weighted random selection. Provide an array of objects with chance and result properties, and a random result will be selected according to the provided chance values.

Installation

NPM: npm install --save weighted-randomly-select

YarnPkg: yarn add weighted-randomly-select

Examples

let Randomly = require("weighted-randomly-select");
 
// Every outcome can be equiprobable
let name = Randomly.select([{
  chance: 1, result: "John"
}, {
  chance: 1, result: "Mary"
}]);
// name will be either "John" or "Mary"
 
// Some outcomes can be more probable than others
let coin = Randomly.select([{
  chance: 1, result: "Heads"
}, {
  chance: 1, result: "Tails"
}, {
  chance: 0.01, result: "Side"
}]);
// coin will be either "Heads", "Tails", or "Side"
 
// Chance values can be any positive number, and result values
// can be anything other than null and undefined
let item = Randomly.select([{
  chance: 0.8, result: { someField: "someValue" }
}, {
  chance: 20, result: 42
}, {
  chance: 1.5, result: [3, 1, 5]
}]);
// item will be either { someField: "someValue" }, 42, or [3, 1, 5]

API Reference

Randomly.select(options)

options: an array of objects, each of which having a chance number value and result value

chance: any positive floating point value (zero is permitted but such an entry will never be selected)

Note: all chance values must add up to a value greater than zero (i.e. there should be something to select). These values do not have to add up to 1 or any other specific value.

Return value: one of the result values in the options array.

Throws errors if any input is invalid.

Randomly.selectWithoutValidation(options)

Same as above but does not perform any validation on the provided input. If you're encountering unexpected issues, try using the above method, which does the same thing but with input validation.