JSFiddle - React, Tailwind, and code Playground
HTML
<div>
<div>
<!-- content -->
<div id="a">content 1 will come here
</div>
</div>
</div>
<div id="b">content 2 will come here<br />content 2 will come here content 2 will come here content 2 will come here content 2 will come here
</div>
CSS
#a, #b{background-color:gray; color:black; margin:5px;0;}
JavaScript
$(document).ready(function(){
$('#b').width($('#a').width());
})