alighn右boostrap4
<div class="float-left">Float left on all viewport sizes</div><br>
<div class="float-right">Float right on all viewport sizes</div><br>
<div class="float-none">Don't float on all viewport sizes</div>
引导显示flex
<div class="d-flex">I'm a flexbox container!</div>
之间的引导空间
<div class="d-flex justify-content-between">...</div>
在类bootstrap之间证明内容空间
<div class="row d-flex justify-content-between"></div>