Add days, hours , mins , sec in date/time field Client Script ServiceNow

var getDate = g_form.getValue('get_date'); //Choose the field to add time from
var addtime = 5; //The amount of time to add
var addtype = 'day'; //The time type. Can be second, minute, hour, day, week, month, year.

var ajax = new GlideAjax('ClientDateTimeUtils');
ajax.addParam('sysparm_name', 'addDateTimeAmount');
ajax.addParam('sysparm_fdt', getDate);
ajax.addParam('sysparm_addtime', addtime);
ajax.addParam('sysparm_addtype', addtype);
ajax.getXMLAnswer(doSomething);

function doSomething(answer){
alert(answer);
}