randomByWeights

introduction

Returns the index based on the array weight probability.

install

npm i randombyweights

use

@param {Array} Probabilitys

@return {Number} Index

const randomByWeights = require('randombyweights');
let randomIndex = randombyweights([3,4,5]); // 0:3/12   1:4/12   2:5/12

eg.

• [1, 1, 1] Return the index 0,1,2 Probability is equal, both are 1/3.

• [5, 1, 3] Return the index 0 probability is 5/9, 1 probability is 1/9, 2 probability is 3/9.

• [2, 94, 3, 1] Returns the index 0 probability is 2%, 1 probability is 94%, 2 probability is 3%, 3 probability is 1%.

• [0.02, 0.94, 0.03, 0.01] is equivalent to the above 2, 94, 3, 1

• Note: not array returns -1 and weight sum is 0 (eg [0, 0, 0]) returns -1