N/util Module
util.isDate(obj)
Method Description: Returns true if the obj parameter is a JavaScript Date object 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.isDate(obj)

// Code Example 1

//Add additional code

//...

var todaysDate = new Date();

util.isDate(todaysDate);    // returns true

util.isDate(new Date());    // returns true



var today = "September 28, 2015";

util.isDate(today);         // returns false

//...

//Add additional code



//SOURCE: https://system.netsuite.com/app/help/helpcenter.nl?fid=section_4434642842.html