js的随机数生成器，不再使用Math.random

先上代码：

var randomNum = (function(){

var today = new Date();

var seed = today.getTime();

function rnd(){

seed = ( seed * 9301 + 49297 ) % 233280;

return seed / ( 233280.0 );

};

return function rand(number){

return Math.ceil(rnd(seed) * number);

};

})();

测试下：

console.log(randomNum(100))

console.log(randomNum(100))

console.log(randomNum(100))

为神马会使用9301，49297和233280这几个数字？原理见这里 http://www.zhihu.com/question/22818104