JS随机生成字符串

var radomStr = new Date().getTime()+getRadomNum(6);
function getRadomNum(capacity){
   var chars = ['0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'];
   var res = "";
   for(var i = 0; i < capacity ; i ++) {
      var id = Math.ceil(Math.random()*chars.length);
      res += chars[id];
   }
   return res;
}