How to append a custom field's value on Events Calendar's title?

Frappe Framework Customization
1

I am trying to add a custom field’s value just after the “subject” in Events Calendar.
event_calendar.js

frappe.views.calendar["Event"] = {
        field_map: {
                "start": "starts_on",
                "end": "ends_on",
                "id": "name",
                "allDay": "all_day",
                "title": "subject" + "custom_field",
                "status": "status",
                "color": "color",
        },
        style_map: {
                "Custom Field Value 1": "success",
                "Custom Field Value 2": "info",
                "Custom Field Value 3": "warning"
        },
        get_events_method: "frappe.desk.doctype.event.event.get_events"
}

I have also tried adding it this way:

frappe.views.calendar["Event"] = {
        field_map: {
                "start": "starts_on",
                "end": "ends_on",
                "id": "name",
                "allDay": "all_day",
                "title": "subject + custom_field",
                "status": "status",
                "color": "color",
        },
        style_map: {
                "Custom Field Value 1": "success",
                "Custom Field Value 2": "info",
                "Custom Field Value 3": "warning"
        },
        get_events_method: "frappe.desk.doctype.event.event.get_events"
}

Now the problem is, that when I migrate and restart bench, I can not see even the title now.
I just want to know how can I add more than one title right after the default title.

I can easily do this while working on Codeigniter/PHP’s FullCalendar but not here on ERPNext.
Any help would be appreciated.
Also, kindly do not redirect me to any other link, I have seen them all, none works.
Thanks.

2

Can you point to a field_map example case that shows what you require is supported?

Does the web console report an error for this?

“Any help would be appreciated.
Also, kindly do not redirect me to any other link, I have seen them all, none works.”

This is suspect to say the least :wink: