Front-endvalideringsfunktion för receptapplikation

function registerValidate() {
    var username = $('#username-input').val();
    var emailAddress = $('#email-input').val();
    var userPassword = $('#password-input').val();
    var userPasswordMatch = $('#password-match-input').val();
    var success = true;
    var pass = {
        "usernameRegistered": true,
        "usernameInvalid": true,
        "emailRegistered": true,
        "emailInvalid": true,
        "passwordsDoNotMatch": true,
        "passwordInvalid": true,
        "incomplete": true
    };
    if(!username)
        pass.incomplete = false;
    else if(!(username.replace(/^(?=.{8,20}$)[a-zA-Z0-9._]+/i, '') === ""))
        pass.usernameInvalid = false;
    if(!emailAddress)
        pass.incomplete = false;
    else if(!(emailAddress.replace(/^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/, '') === ""))
        pass.emailInvalid = false;
    if(!userPassword)
        pass.incomplete = false;
    else if(userPassword.length < 8)
        pass.passwordInvalid = false;
    if(!userPasswordMatch)
        pass.incomplete = false;
    else if(userPassword != userPasswordMatch)
        pass.passwordsDoNotMatch = false;
    if(pass.incomplete) {
        $.post({
            url: "credentialsInUse.cgi",
            data: {
                emailAddress: emailAddress,
                username: username
            },
            dataType: "json",
            async: false,
            success: function(data) {
                pass.emailRegistered = data.emailRegisteredPass;
                pass.usernameRegistered = data.usernameRegisteredPass;
            }
        });
    }
    Object.keys(pass).forEach(function(key) {
        var selector = "#error-" + key.toLowerCase();
        if(pass[key])
            $(selector).css('display', 'none');
        else {
            $(selector).css('display', 'list-item');
            success = false;
        }
    });
    if(success)
        $('#error-container').css('display', 'none');
    else
        $('#error-container').css('display', 'inline-block');
    return success;
}