Basic Dropdown
A dropdown menu is a toggleable menu that allows the user to choose one value from a predefined list
Dropdown Divider
The
                                .dropdown-divider class is used to separate links inside the dropdown menu with a thin horizontal border
                            
Dropdown Header
The
                                .dropdown-header class is used to add headers inside the dropdown menu
                            
Disable and Active items
The
                                .dropdown-header class is used to add headers inside the dropdown menu
                            
Button Dropdowns
Dropup
The
                                .dropup class makes the dropdown menu expand upwards instead of downwards
                            
Dropright
Trigger dropdown menus at the right of the elements by adding
                                .dropend to the parent element
dropstart
Trigger dropdown menus at the right of the elements by adding
                                .dropstart  to the parent element
