Dropdowns
Single button dropdowns
Any single .btn can be turned into a dropdown
                                                toggle with some markup changes. Here’s how you can put them to work
                                                with either <button>
                                                elements:
Variant
The best part is you can do this with any button variant, too:
Split button dropdowns
The best part is you can do this with any button variant, too:
Sizing
Button dropdowns work with buttons of all sizes, including default and split dropdown buttons.
Dropup variation
Trigger dropdown menus above elements
                                                by adding .dropup to the parent
                                                element.
Menu alignment
Add .dropdown-menu-right
                                                to a .dropdown-menu to right
                                                align the dropdown menu.
Dropright variation
Trigger dropdown menus at the right of the elements by adding .dropright to the parent element.
                                            
Dropleft variation
Trigger dropdown menus at the right of the elements by adding .dropleft to the parent element.