Adding a button to item sublist using UE

Solution

define(['N/ui/serverWidget'],
    /**
 * @param{serverWidget} serverWidget
 */
    (serverWidget) => {
        /**
         * Defines the function definition that is executed before record is loaded.
         * @param {Object} scriptContext
         * @param {Record} scriptContext.newRecord - New record
         * @param {string} scriptContext.type - Trigger type; use values from the context.UserEventType enum
         * @param {Form} scriptContext.form - Current form
         * @param {ServletRequest} scriptContext.request - HTTP request information sent from the browser for a client action only.
         * @since 2015.2
         */
   
        const itemGroupForm = '149'; //JJ Expertec Estimate item group internal ID
        const beforeLoad = (scriptContext) => {
            try{
                let currRec=scriptContext.newRecord;
                let currentForm=currRec.getValue({
                    fieldId:'customform'
                })
                if ((scriptContext.type == scriptContext.UserEventType.CREATE||
                    scriptContext.type == scriptContext.UserEventType.EDIT)&& currentForm == itemGroupForm) {
                  
                  // Get the form object
                  const form = scriptContext.form;
                  
                  // Get the Items sublist
                  let sublist = form.getSublist({
                    id: "item"
                  });
                  
                  // Add the custom button to the sublist
                  let showPdfButton = sublist.addButton({
                    id: "custpage_showpdf_button",
                    label: "Check All Show PDF",
                    functionName: "enableShowPdf"
                  });
                  
     
                }
              }catch(e)
              {
                  log.error("err@beforeLoad",e.message)
              }
              

        }

        return {beforeLoad}

    });