bootstrap 4中导航的右侧部分

<ul class="navbar-nav ml-auto">
  <li class="nav-item">
    <a class="nav-link" href="#">链接1</a>
  </li>
  <li class="nav-item">
    <a class="nav-link" href="#">链接2</a>
  </li>
</ul>

<form class="form-inline">
  <input class="form-control mr-sm-2" type="search" placeholder="搜索" aria-label="搜索">
  <button class="btn btn-outline-success my-2 my-sm-0" type="submit">搜索</button>
</form>

<ul class="navbar-nav ml-auto">
  <li class="nav-item">
    <a class="nav-link" href="#">登录</a>
  </li>
  <li class="nav-item">
    <a class="nav-link" href="#">注册</a>
  </li>
</ul>

<ul class="navbar-nav ml-auto">
  <li class="nav-item dropdown">
    <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
      下拉菜单
    </a>
    <div class="dropdown-menu" aria-labelledby="navbarDropdown">
      <a class="dropdown-item" href="#">选项1</a>
      <a class="dropdown-item" href="#">选项2</a>
      <div class="dropdown-divider"></div>
      <a class="dropdown-item" href="#">其他</a>
    </div>
  </li>
</ul>