<script>

function passCounter()
{
var counterDiv = document.getElementById('counter');
var passLength = document.loginForm.newPass.value.length;
var newPass = document.loginForm.newPass.value;
var pasConfirm = document.loginForm.newPassConfirm.value;

counterDiv.innerHTML = "<b style='font-size: 9px;'>" + passLength + "</b>";

for (var i = 1; i <= document.loginForm.newPass.value.length; i++)
{
counterDiv.innerHTML += "a";
}

if(passLength >= 8)
{
counterDiv.innerHTML = "<b style='color: #99cc33; font-size: 10px;'>Wpisane hasło ma odpowiednią długość!</b>";
}

if(newPass != pasConfirm)
{
document.getElementById('confirmation').innerHTML = "<b style='color: red; font-size: 10px;'>Potwiedzenie nowego hasła jest inne!</b>";
document.loginForm.mySub.disabled = true;
}
else
{
document.getElementById('confirmation').innerHTML = "<b style='color: #99cc33; font-size: 10px;'>Potwiedzenie OK!</b>";
document.loginForm.mySub.disabled = false;
}
}

</script>
      
      
<form name="loginForm" method="POST" action="chgPass.php">
<input type="password" name="newPass" maxlength="15" onKeyUp="passCounter()">
<div id="counter"></div>
<input type="password" name="newPassConfirm" maxlength="15" onKeyUp="passCounter()">
<div id="confirmation"></div>
</form>

function passStrength(pass){
var w = [.25, .25, .25, .25]; // wagi
var s = 0; // sila
// ad. 1
if( pass.length > 7 ) s += w[0];
// ad. 2
if( pass.toLowerCase() != pass && pass.toUpperCase() != pass ) s += w[2];
// pozostale dwa warunki dopisz sam
return s;
}