bootstrap flexible columns code example
Example 1: bootstrap 4 center div
<div class="d-flex justify-content-start">...</div>
<div class="d-flex justify-content-end">...</div>
<div class="d-flex justify-content-center">...</div>
<div class="d-flex justify-content-between">...</div>
<div class="d-flex justify-content-around">...</div>
Example 2: .row bootstrap
.row{
display: flex;
flex-wrap: wrap;
margin-right: -15px;
margin-left: -15px;
}