돈십만원 쥐어 주시면 제가 10분안에 만들어 드리겠습니다....
ㅜㅜ 공부하시면 쉽습니다

<script>
function RndStr() {
this.str = '';
this.pattern = /^[a-zA-Z0-9]+$/;

this.setStr = function(n) {
if(!/^[0-9]+$/.test(n)) n = 0x10;
this.str = '';
for(var i=0; i<n-1; i++) {
this.rndchar();
}
}

this.setType = function(s) {
switch(s) {
case '1' : this.pattern = /^[0-9]+$/; break;
case 'A' : this.pattern = /^[A-Z]+$/; break;
case 'a' : this.pattern = /^[a-z]+$/; break;
case 'A1' : this.pattern = /^[A-Z0-9]+$/; break;
case 'a1' : this.pattern = /^[a-z0-9]+$/; break;
default : this.pattern = /^[a-zA-Z0-9]+$/;
}
}

this.getStr = function() {
return this.str;
}

this.rndchar = function() {
var rnd = Math.round(Math.random() * 1000);
if(!this.pattern.test(String.fromCharCode(rnd))) {
this.rndchar();
} else {
this.str += String.fromCharCode(rnd);
}
}
}

var rndstr = new RndStr();

rndstr.setType('a1');
rndstr.setStr(11);
document.write(rndstr.getStr() + "<br />");

rndstr.setType('A1');
rndstr.setStr(11);
document.write(rndstr.getStr() + "<br />");
</script>

이미 러셀러 파트너 베너 시스템에 있는 기능이라죠?ㅎㅎㅎㅎ