Concatenate date and time in a variable

I need to create a complete date with date and time, I have two functions that receive a date and another time and I want to concatenate them to show the following format: yyyy-MM-dd HH:mm:ss

dateChange(selectedDate) {
   //console.log(selectedDate);
   const date = '${selectedDate.year}-${selectedDate.month}-${selectedDate.day}';
   console.log(this.data);}
}

onChange() {
   console.log(this.hourTime);
}