N/file Module
File.isText
Property Description: Indicates whether a file type is text-based. This property is read-only.
Type: boolean
Supported Script Types: Server-side scripts For more information, see SuiteScript 2.0 Script Types.
Module: N/file Module
Since: 2015.2
Search NetSuite - https://system.netsuite.com/app/help/helpcenter.nl?search=File.isText

// Code Example 1

//Add additional code

//...

var fileObj = file.load({

    id: 145

});

if (fileObj.isText === true){

    ...

}

//...

//Add additional code



//SOURCE: https://system.netsuite.com/app/help/helpcenter.nl?fid=section_4229267767.html