Hi,

you are doing stringify() so it would come as string to client script

don't parse it; directly use

var iterationVal = "22";

var ajax = new GlideAjax('SetFieldValues');
ajax.addParam('sysparm_name', 'setRecordValues');
ajax.addParam('sysparm_iteration', iterationVal);
ajax.getXML(getReturnValue);

function getReturnValue(response) {

    var answer = response.responseXML.documentElement.getAttribute("answer");
    
    g_form.addInfoMessage(answer);

}

Regards
Ankur