flex box in bootstrap4 code example
Example 1: bootstrap justify-content-center for md
<div class="row justify-content-md-center"></div>
Example 2: bootstrap display flex
<div class="d-flex">I'm a flexbox container!</div>
Example 3: Bootstrap 4 Flex
<div class="d-flex p-3 bg-secondary text-white">
<div class="p-2 bg-info">Flex item 1</div>
<div class="p-2 bg-warning">Flex item 2</div>
<div class="p-2 bg-primary">Flex item 3</div>
</div>