for (letter of ['letter1', 'letter2', 'letter3']) {
        var sContent = "<!-- Original XML doc file for sign example. -->";
        // Создаем объект CAdESCOM.SignedXML
        var oSignedXML = yield cadesplugin.CreateObjectAsync("CAdESCOM.SignedXML");
        yield oSignedXML.propset_Content(sContent);

        // Указываем тип подписи - в данном случае по шаблону
        yield oSignedXML.propset_SignatureType(cadesplugin.CADESCOM_XML_SIGNATURE_TYPE_TEMPLATE);

        var sSignedMessage = "";
        try {
            sSignedMessage = yield oSignedXML.Sign(oSigner);
        } catch (err) {
            alert("Failed to create signature. Error: " + cadesplugin.getLastError(err));
            return;
        } 
}