Generate a weighted random number

random-with-weight.js

// Source: https://stackoverflow.com/a/8435261
function weightedRand(spec) {
    let i, j, table = [];

    for (i in spec) {
        // The constant 10 below should be computed based on the
        // weights in the spec for a correct and optimal table size.
        // E.g. the spec {0:0.999, 1:0.001} will break this impl.
        for (j = 0; j < spec[i] * 10; j++) {
            table.push(i);
        }
    }

    return function() {
        return table[Math.floor(Math.random() * table.length)];
    }
}
 
// weightedRand({
//     0: 0.8, 
//     1: 0.1, 
//     2: 0.1
// });