Script for checking password strength

The solution depends on your exact requirements and the context. In your case, you could simplify the if-condition like below. If all fit into one if, you can write your code block there only once. If you need it and can't unify your condition, make it a function.

Here, I'm using a combined approach. I put the code from your if into a function, jQuery objects are cached and don't have to be recreated (but are still protected from outside modification because they only exist inside the scope of that function). And I combined all the conditions I could see in your example.

var indicateBadPassword = (function() {
        var $passwordStrength = $('.passwordStrength'),
            $password = $('#password'),
            $passwordStrengthInfo = $('.passwordStrenghtInfo');
        return function() {
            $passwordStrength.
                animate({width:'75px',height:'5px'},200).
                show().
                css('background-color',red);
            $password.css('border-color',green);
            $passwordStrengthInfo.text(weak).show();
            passwordErrors = true;

        }
    })();
if (lessThan12Password && (passwordLC || passwordUC || passwordN)) {
    indicateBadPassword();
}