Glide Ajax helps us to call from client-side to server-side code. By this example, we can check particular user is part of a specific group from the client side.

Client-Side (Client Script) Asynchronous Ajax: 

 var ga = new GlideAjax('Get_group_member');
 ga.addParam('sysparm_name', 'getMemberof');
 ga.addParam('sysparm_user', newValue);
 ga.addParam('sysparm_group', 'SN-AD-Group');
 ga.getXML(getData);

 function getData(response) {
   var answer = response.responseXML.documentElement.getAttribute("answer");
   if (answer == 'false'){
			// nothing
    }else{
     g_form.addErrorMessage('is part of group mamaber');
     g_form.clearValue('userid');
     }
  }

Synchronous Ajax:

getXMLWait() is not available to scoped applications and service portal.

var ga = new GlideAjax('Get_group_member');
ga.addParam('sysparm_name', 'getMemberof');
ga.addParam('sysparm_user', newValue);
ga.addParam('sysparm_group', 'SN-AD_PCI_Disabled_Group');
ga.getXMLWait();
alert(ga.getAnswer());

Server Side (Script Include): getMemberof function – single value return

getMemberof: function() {
 var user = this.getParameter('sysparm_user');
 var group = this.getParameter('sysparm_group');
 var enq='group.name=' + group + '^user=' + user;
 var gr = new GlideRecord('sys_user_grmember');
 gr.addEncodedQuery(enq);
 gr.query();
 if (gr.next()) {
   return true;
 } else {
   return false;
   }
 },

Check out the video for more details: