Magento 1.9 – Change Error Message on Login Page

In your theme folder create a locale/[locale_code]/translate.csv file.

Example: app/design/frontend/[package]/[theme]/locale/en_US/translate.csv

And add this line:

"Please make sure your passwords match.","Translated String."

And finally refresh Translations cache.

You can use below regular expression.

(/^(?=.*\d)(?=.*[a-z])(?=.*[A-Z])[0-9a-zA-Z]{8,}$/)

Explanation of this expression is

(/^
(?=.*\d)                //should contain at least one digit
(?=.*[a-z])             //should contain at least one lower case
(?=.*[A-Z])             //should contain at least one upper case
[a-zA-Z0-9]{8,}         //should contain at least 8 from the mentioned characters
$/)

You can replace line

 return !(pass.length>0 && pass.length < 8);

with

if (!(/^(?=.*[0-9])(?=.*[a-z])(?=.*[A-Z])([a-zA-Z0-9]{8,})$/.test(pass))) {
        return false;
}
return true;

And change error message related to expression. You can do same for admin password.

For special character you can use below regular expression.

Minimum 8 characters at least 1 Uppercase Alphabet, 1 Lowercase Alphabet, 1 Number and 1 Special Character from amongst these $@$!%*?&#^ .

"^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[$@$!%*?&])([A-Za-z\d$@$!%*?&#^]{8,})"

You can use it like this way

if (!(/^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[$@$!%*?&#^])([A-Za-z\d$@$!%*?&#^]{8,})$/.test(pass))) {
     return false;
} 
return true;