Custom Script not working (get date)

Frappe Framework Custom Script
1

I have the following problem, I need to get only the day and month value from one field (date_joining) and insert it in another field (date_entry), I have the following code, but it doesn’t work:

frappe.ui.form.on(‘Employee’, function(frm) {

var date1 = new Date(frm.doc.date_of_joining);
			
	final1 = (date1.getDay() && date1.getMonth());	
	frm.set_value('date_entrada',final1);
	

}

)

thanks