GlideDateTime(date).setDayOfMonthUTC(1) returns undefined when run via a Script Include - platform bug?

[JeremiP]

Why in Script Includes, using the .setDayOfMonthUTC(int) method on GlideDateTime(datetime) objects return undefined, while it's working okay outside of the Script Include?

What I run in the Scripts - Background module:

var util = new u_gdt();
var date = util.dateDebug('2020-04-22 21:07:27');

var dt = new GlideDateTime('2020-04-22 21:07:27');
gs.info("var dt = new GlideDateTime(date): "+dt);
dt.setDayOfMonthUTC(1);
gs.info("dt.setDayOfMonthUTC(1): "+dt);

The Script Include is as follows:

var u_gdt = Class.create();
u_gdt.prototype = {
    initialize: function() {},
    dateDebug: function(dateTime) {
        var service_date = new GlideDateTime(dateTime);
        var now = new GlideDateTime();
        gs.info([, "service_date = new GlideDateTime(dateTime): " + service_date,
                "service_date.isValid(): " + service_date.isValid(),
                "service_date.getDaysInMonthUTC(): " + service_date.getDaysInMonthUTC(),
                "service_date.setDayOfMonthUTC(1): " + service_date.setDayOfMonthUTC(1),
                "now = new GlideDateTime(): " + now,
                "now.setDayOfMonthUTC(1): " + now.setDayOfMonthUTC(1)
				].join('\n'));
        return service_date;
    },
    type: 'u_gdt'
};

Returns when ran:

*** Script: 
service_date = new GlideDateTime(dateTime): 2020-04-22 21:07:27
service_date.isValid(): true
service_date.getDaysInMonthUTC(): 30
service_date.setDayOfMonthUTC(1): undefined
now = new GlideDateTime(): 2020-04-21 12:42:54
now.setDayOfMonthUTC(1): undefined
*** Script: var dt = new GlideDateTime(date): 2020-04-22 21:07:27
*** Script: dt.setDayOfMonthUTC(1): 2020-04-01 21:07:27

Compare the returns of service_date. / now.setDayOfMonthUTC(1) and dt.setDayOfMonthUTC(1).

[Michael Fry1]

Does your script includes have Client Callable checked?

If yes, you need to remove the line below:

    initialize: function() {},

[JeremiP]

Hi Michael,

That's a good guess, but Client Callable is unchecked. I created this script on my PDI after I noticed this behavior on a consumer instance.

Just to be sure, I've toggled the checkmark and removed the line like you suggested, but the behavior's still the same.

[JeremiP · Accepted solution]

It's been my mistake!

When I ran it out of the Script Include, I first ran the method, and then misleadingly echoed the object to the console in a separate call:

dt.setDayOfMonthUTC(1);
gs.info("dt.setDayOfMonthUTC(1): "+dt);

//vs:

gs.info("dt.setDayOfMonthUTC(1): "+dt.setDayOfMonthUTC(1));

The latter line results in the same behavior, returning undefined - and that's actually in the docs after all:

https://developer.servicenow.com/dev.do#!/reference/api/newyork/server/no-namespace/c_APIRef#r_ScopedGlideDateTimeSetDayOfMonthUTC_Number_day

Return:

Type	Description
void	Method does not return a value