Korrekt måde at anvende jquery

var login_callback = function(result) {
    if (typeof result.action !== 'undefined' && typeof result.data !== 'undefined') {
        if (result.action === 'login_form') {
            var loginForm = ""
            loginForm += '<form name=\"login\" id=\"login\" action=\"/\" method=\"post\">'
            loginForm += '  <div>'
            loginForm += '    <input size=\"20\" type=\"text\" maxlength=\"30\" name=\"username\" value=\"\"><br>'
            loginForm += '    <input size=\"20\" type=\"password\" maxlength=\"20\" name=\"password\" value=\"\"><br>'
            loginForm += '    <input type=\"submit\" name=\"submit\" value=\"log ind\">'
            loginForm += '  </div>'
            loginForm += '</form>'
            $('#loginbox').html(loginForm);
        } else if (result.action === 'try_again') {
            var tryAgain = ""
            tryAgain += '<span class=\"error_text\">'
            tryAgain += '  Forkert brugernavn eller adgangskode.<br>'
            tryAgain += '</span>'
            tryAgain += '<br>'
            tryAgain += '<a href=\"/\">Prøv igen</a>'
            $('#loginbox').html(tryAgain);
        } else if (result.action === 'logout') {
            var logOut = ""
            logOut += '<h3>'
            logOut += '  Velkommen '+html(result.data)+'!'
            logOut += '</h3'
            logOut += '<br>'
            logOut += '<a href=\"/\">Log ud</a>'
            $('#loginbox').html(logOut);
        }
    }
};