Hi,

See sample code:

gb = new GlideAjax('HMgetSubCat2');

  gb.addParam('sysparm_name', 'getSubCat');

  gb.addParam('sysparm_category', oldValue);

  gb.getXML(function(response) {

  var answerA = gb.getAnswer();

  var objA = JSON.parse(answerA);

  console.log('JC Debug answer='+answerA);

  for(var j=0; j<objA.length; j++){

  console.info("JC Debug Remove Option: " + objA[j].value);

  g_form.removeOption('u_subcategory',objA[j].value);

  }

  });

Links:

https://community.servicenow.com/community?id=community_question&sys_id=7db05f69dbdcdbc01dcaf3231f961929&view_source=searchResult

https://community.servicenow.com/community?id=community_question&sys_id=bbc9d0d7db10db00852c7a9e0f961972&view_source=searchResult

Thanks,
Ashutosh Munot