N/error Module
error.UserEventError
Object Description: Encapsulates a custom SuiteScript error for a user event script. Use this object in a try-catch statement to abort script execution. Create a new custom error with the error.create(options) method. The error.create(options) method returns error.UserEventError when it is called in a user event script. When error.create(options) is called in a server script that is not a user event script, it returns error.SuiteScriptError. For a complete list of this object’s methods and properties, see UserEventError Object Members.
Supported Script Types: User event scripts For more information, see SuiteScript 2.0 User Event Script Type.
Module: N/error Module
Since: 2015.2
Search NetSuite - https://system.netsuite.com/app/help/helpcenter.nl?search=error.UserEventError

// Code Example 1

//Add additional code

//...

// Include this code in a user event script to create an error.UserEventError object

var UEcustom_error = error.create({

    name: 'MY_ERROR_CODE',

    message: 'my custom UserEventError details',

    notifyOff: false

});

//...

//Add additional code



//SOURCE: https://system.netsuite.com/app/help/helpcenter.nl?fid=section_4253440386.html