Bootstrap 4:将输入水平放置

<form class="form-inline">
  <label class="sr-only" for="name">Name</label>
  <input type="text" class="form-control mb-2 mr-sm-2" id="name" placeholder="Name">

  <label class="sr-only" for="email">Email</label>
  <input type="email" class="form-control mb-2 mr-sm-2" id="email" placeholder="Email">

  <button type="submit" class="btn btn-primary mb-2">Submit</button>
</form>

<div class="input-group mb-3">
  <input type="text" class="form-control" placeholder="Username" aria-label="Username" aria-describedby="basic-addon2">
  <div class="input-group-append">
    <button class="btn btn-outline-secondary" type="button">Button</button>
  </div>
</div>