Weighted Sampling Generator

weighted_generator.js

function rand (max) { return Math.random() * max; }

function *randomSample () {
    var answer = yield;
    var totalWeight = answer.w;
    while (true) {
        var next = yield answer;
        var w = next.w;
        var r = rand(totalWeight + w);

        if (r > totalWeight) {
            answer = next;
        }
        totalWeight += w;
    }
}

var sample = randomSample();
var v, i = 1000;
sample.next();

while (i--) {
  v = sample.next({n: 'elem' + i, w: rand(10)}).value;
}

console.log(v);