var d = new Date(transDueDate);
    var newDueDate = d.setDate(d.getDate() + transTerms);
   
    var newAcceptableDate = format.format({
      value: newDueDate,
      type: format.Type.DATE
    })

  
    curRec.setValue({
      fieldId: 'duedate',
      value: newAcceptableDate,
      ignoreFieldChange: true
      // opcional, o padrão é falso
    });

define(["N/record", "N/render", "N/format]

/**
 *@NApiVersion 2.x
 *@NScriptType UserEventScript
 */
define(['N/record', 'N/format', 'N/render'], function (record, format, render) {

  function beforeLoad(context) {

  }

  function beforeSubmit(context) {

  }

  function afterSubmit(context) {

    //load record
    var curRec = context.newRecord; //can substitute "context.oldRecord", or "currentRecord.get();"
  
    //get current due date
    var transDueDate = curRec.getValue({fieldId: 'duedate'});
  
    //get the terms, this will likely come as an internal id. use getText if you want the text.
    var transTerms = curRec.getValue({fieldId: 'terms'});
  
    //empty string to hold terms as a number of days
    var addtlDays;
  
    //transform the internal id to terms as a number of days
    switch (transTerms){
      case 1: // Ex: 1 = internal id for term "Net 15"
        addtlDays = 15;
        break;
  
      case 2: // Ex: 2 = internal id for term "Net 30"
        addtlDays = 30;
        break;
  
      //add additional case statements as needed
  
      default:
        addtlDays = 0;
    }
  
    //calculuate the new due date
    var d = new Date(transDueDate);
    var newDueDate = d.setDate(d.getDate() + addtlDays);

    var NewAcceptableDate = format.format({
      value: newDueDate,
      type: format.Type.DATE
    })
  
    //set the new due date
    curRec.setValue({
      fieldId: 'duedate',
      value: newAccept,
      ignoreFieldChange: true //optional, default is false
    });
  }

  return {
    beforeLoad: beforeLoad,
    beforeSubmit: beforeSubmit,
    afterSubmit: afterSubmit
  }
});