Generating pseudo-random numbers in js

Occasional curious generate random numbers, so a look online. In the know almost saw a more powerful answer, but also learned a little knowledge. There is also given a random number generation function, but also talked about some of the principle of generating random numbers, including why you want to use 9301,49297,233280 these three numbers to generate random numbers.
The following is known almost Links: https://www.zhihu.com/question/22818104

js generated bit random number

rand = (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);
    return Math.ceil(rnd() * number);
  };
})();
myNum = (rand(5));
console.log(myNum);