JSFiddle - React, Tailwind, and code Playground

HTML

<div id='container'>
    <div class='child'>Content</div>
    <div class='child'>Content</div>
    <div class='child'>Content</div>
    <div class='child'>Content</div>   
</div>

CSS

.child{
    height: 40px;
    background-color: red;
}
#container{
    height: 120px;
    background-color: gray;
    padding: 5px;
}

JavaScript

var childHeight = 0
$('.child').each( function() {
    childHeight = childHeight + $(this).height();
})
$('#container').height(childHeight);