boostrap icon button code example
Example 1: bootstrap 4 button with icon
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
<button class="btn"><i class="fa fa-home"></i></button>
Example 2: heart button bootstrap
<button type="button" class="btn btn-default" aria-label="Left Align">
<span class="glyphicon glyphicon-align-left" aria-hidden="true"></span>
</button>
<button type="button" class="btn btn-default btn-lg">
<span class="glyphicon glyphicon-star" aria-hidden="true"></span> Star
</button>