N/currentRecord Module
CurrentRecord.getSublistValue()
Method Description: Returns the value of a sublist field. Gets a numeric value for rate and ratehighprecision fields.
Returns: number | Date | string | array | boolean
Supported Script Types: Client scripts For more information, see SuiteScript 2.0 Client Script Type.
Governance: None
Module: N/currentRecord Module
Since: 2016.2
Search NetSuite - https://system.netsuite.com/app/help/helpcenter.nl?search=CurrentRecord.getSublistValue(options)

// Code Example 1

//Add additional code

//...

var quantity = record.getSublistValue({

    sublistId: 'item',

    fieldId: 'quantity',

    line: 0

});

//...

//Add additional code



//SOURCE: https://system.netsuite.com/app/help/helpcenter.nl?fid=section_4637583237.html