按给定几率进行随机抽取的js代码

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];
}
};
}