<script language="JavaScript" type="text/javascript">
with (document) {
  writeln('<div>Какие символы вы хотите использовать при генерации: <form name=pass_form></div>' +
  '<div style="margin-top:5px;"><input name="upper" type="checkbox"> Заглавные буквы</div>' +
  '<div style="margin-top:5px;"><input name="lower" type="checkbox"> Буквы маленькие</div>' +
  '<div style="margin-top:5px;"><input name="digit" type="checkbox"> Цифры</div><div style="margin-top:5px;">Количество символов: </div>' +
  '<select name="numbers"><option value="6" selected>6</option>');
  for (j = 5; j <= 50; j++) { writeln('<option value=' + j + '>' + j + '</option>'); }
  writeln('</select><br><br><input type="button" value="Выполнить генерирование" onClick=generate()>' +
  '<br><br>Пароль: <input name="getback" size="60" type="text" value=""></form>');
}
upp = new Array('','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');
low = new Array('','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');
dig = new Array('','0','1','2','3','4','5','6','7','8','9');
   
function rnd(x,y,z) {
  var num;
  do {
  num = parseInt(Math.random()*z);
  if (num >= x && num <= y) break;
  } while (true);
return(num);
}
   
function gen_pass() {
var pswrd = '';
var znak, s;
var k = 0;
var n = document.pass_form.numbers.value;
var pass = new Array();
var w = rnd(35,85,105);
for (var r = 0; r < w; r++) {
  if (pass_form.upper.checked) { znak = rnd(1,26,100); pass[k] = upp[znak]; k++; }
  if (pass_form.lower.checked) { znak = rnd(1,26,100); pass[k] = low[znak]; k++; }
  if (pass_form.digit.checked) { znak = rnd(1,10,100); pass[k] = dig[znak]; k++; }
}
for (var i = 0; i < n; i++) {
  s = rnd(1,k-1,100);
  pswrd+= pass[s];
}
document.pass_form.getback.value = pswrd;
}
   
function generate() {
if (pass_form.upper.checked || pass_form.lower.checked || pass_form.digit.checked)
  { gen_pass(); }
else { alert('Выберите тип символов!'); pass_form.upper.checked = true; }
}
</script>