Dropdowns
Basic dropdown
Wrap the dropdown’s toggle (your button or link) and the dropdown menu within .dropdown
Dropdown outline
Add class .btn-outline-{color} to the button inside .dropdown
Dropdown menu
Split button dropdowns
Wrap two buttons in .btn-group and add .dropdown-toggle-split to the toggling button
Icon dropdowns
Add icon tags instead of text
Dropup variation
Add class .dropup
Dropdown sizes
Add class .btn-{size} to dropdown buttons