GlideAjax example servicenow

Server Side Script Include:

var GetEmailAddress = Class.create();
// Extend the global.AbstractAjaxProcessor class
GetEmailAddress.prototype = Object.extendsObject(global.AbstractAjaxProcessor,{
 // Define the getEmail function.  
 // Create a GlideRecord for the User table.
 // Use the sysparm_userID passed from the client side to retrieve a record from the User table.
 // Return the email address for the requested record
 getEmail: function() {
  var userRecord = new GlideRecord("sys_user");
  userRecord.get(this.getParameter('sysparm_userID'));
  return userRecord.email + '';
 },
 type: 'GetEmailAddress'
});

client script to call the GlideAjax:

function onChange(control, oldValue, newValue, isLoading, isTemplate) {

 // Modified the if to return if the newValue == oldValue to avoid
 // unecessary trips to the server
 if (isLoading || newValue === '' || newValue == oldValue) {
  return;
 }

 // Instantiate the GetEmailAddress Script Include 
 var getEmailAddr = new GlideAjax('GetEmailAddress');
 // Specify the getEmail method
 getEmailAddr.addParam('sysparm_name','getEmail');
 // Pass the Requested for sys_id
 getEmailAddr.addParam('sysparm_userID', g_form.getValue('u_requested_for'));
 // Send the request to the server
 getEmailAddr.getXML(populateEmailField);


 // When the response is back from the server
 function populateEmailField(response){
  // Extract the email address from the response, clear any value from the email field, 
  // set new value in the email field
  var emailFromScriptInclude = response.responseXML.documentElement.getAttribute("answer");
  g_form.clearValue('u_requested_for_email');
  g_form.setValue('u_requested_for_email',emailFromScriptInclude);
 }
}