N/file Module
File.save()
Method Description: Method used to: Upload a new file to the NetSuite File Cabinet. Save an updated file to the NetSuite File Cabinet. The File.save() method streams files of any size, provided that the file to save or upload meets File Cabinet limits. If you want to save the file to the NetSuite File Cabinet, you must set a NetSuite File Cabinet folder with the File.folder property. You must do this before you call File.save().
Returns: The internal ID of the file as a number.
Supported Script Types: Server-side scripts For more information, see SuiteScript 2.0 Script Types.
Governance: 20 units
Module: N/file Module
Since: 2015.2
Search NetSuite - https://system.netsuite.com/app/help/helpcenter.nl?search=File.save()

// Code Example 1

//Add additional code

//...

var fileObj = file.create({

    name    : 'test.txt',

    fileType: file.Type.PLAINTEXT,

    contents: 'Hello World\nHello World'

    });

fileObj.folder = 30;

var fileId = fileObj.save();

//...

//Add additional code



//SOURCE: https://system.netsuite.com/app/help/helpcenter.nl?fid=section_4229271179.html