flex direction bootstrap 3 code example
Example 1: align items center bootstrap
<div class="d-flex align-items-start">...</div>
<div class="d-flex align-items-end">...</div>
<div class="d-flex align-items-center">...</div>
<div class="d-flex align-items-baseline">...</div>
<div class="d-flex align-items-stretch">...</div>
Example 2: bootstrap display flex
<div class="d-flex">I'm a flexbox container!</div>