lottery.js

var lottery = function(data, rate, times){
	var source = [];
	rate = rate || (function(){
		var i, rate;
		i = data.length;
		rate = [];
		while(i--){
			rate.push(1);
		}
		return rate;
	}());
	times = times || 10;
	data.forEach(function(value, i){
		var len = rate[i] * times;
		while(len--){
			source.push(value);
		}
	});
	source.sort(function(){
		return 0.5 - Math.random();
	});
	return source[parseInt(Math.random() * source.length, 10)];
};

// Test
lottery(["foo", "bar", "baz"], [1, 8, 16], 10);