给div一个class “dropdown”，将下拉菜单放在这个div里就可以显示bootstrap的下拉菜单。

<div>

            <button type="button" data-toggle="dropdown">

                Dropdown

                <span></span>

            </button>

            <ul role="menu" aria-labelledby="dropdownMenu1">

                <li role="presentation"><a role="menuitem" tabindex="-1" href="#">Regular link</a></li>

                <li role="presentation"><a role="menuitem" tabindex="-1" href="#">Disabled link</a></li>

                <li role="presentation"><a role="menuitem" tabindex="-1" href="#">Another link</a></li>

            </ul>

        </div>