<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>