N/util Module
util.isString(obj)
Method Description: Returns true if the obj parameter is a JavaScript String object or primitive, and false otherwise
Returns: boolean
Supported Script Types: All script types For more information, see SuiteScript 2.0 Script Types.
Governance: None
Module: N/util Module
Since: 2016.1
Search NetSuite - https://system.netsuite.com/app/help/helpcenter.nl?search=util.isString(obj)

// Code Example 1

//Add additional code

//...

util.isString('');                            // returns true

util.isString('a string');                    // returns true



var myString = new String('another string');

util.isString(myString);                      // returns true



util.isString(null);                          // returns false

//...

//Add additional code



//SOURCE: https://system.netsuite.com/app/help/helpcenter.nl?fid=section_4434798099.html