【备忘】按给定几率进行随机抽取

function StringResource(k) { return StringResource[k] || k; }
function RandomSelector() {
  var f = 0, c = [];

  return function (v, r) {
    if (arguments.length) {
      if (r <= 0) throw { message: StringResource("INVALID_ARGUMENT") };
      c.push([r, v]);
      f += r;
    } else {
      var i = 0; r = Math.random() * f;
      for (; ; ) if ((r -= (v = c[i++])[0]) < 0) return v[1];
    }
  };
}

没啥技术含量的随机抽取