Here an example how to get dynamic Sys_id with ajax in serviceNow

You Have to create script include named getRecordSysIdByName and then you can call it in your controller or your ui page

var getRecordSysIdByName = Class.create();

getRecordSysIdByName.prototype = Object.extendsObject(AbstractAjaxProcessor,{

file: function(){

return this.getSysId('sys_attachment');

},

css: function(){

return this.getSysId('content_css');

},

uiPage: function(){

return this.getSysId('sys_ui_page');

},

getSysId: function(tableName){

var recordName = this.getParameter('sysparm_record_name');

var ga = new GlideRecord(tableName);

ga.get('name',recordName);

gs.log('sys id: '+ga.sys_id);

return ga.sys_id;

}

});

in your controller:

var pageName = "test_template_menu";

var ga = new GlideAjax('getRecordSysIdByName');

ga.addParam('sysparm_name', 'uiPage');

ga.addParam('sysparm_record_name', pageName);

ga.getXMLWait();

$scope.uiPage = {

name: pageName,

sys_id: ga.getAnswer(),

url: 'ui_page.do?sys_id='+ga.getAnswer()

};