JSFiddle - React, Tailwind, and code Playground

HTML

<div class="flexList">
  <div class="flexItem"></div>
  <div class="flexItem"></div>
  <div class="flexItem"></div>
</div>

CSS

.flexList {
  display: flex;
}

.flexItem {
  padding: 10px;
  margin: 0 5px;
  flex: 1 1 calc(33% - 10px);
  
  background: #000;
}

JavaScript

$(window).on('load resize', function(){
	
  var flexItem = $('.flexItem');

  flexItem.each(function(index, item){

    var item = $(item);
    var itemWidth = item.width();

    item.height(itemWidth);

  });
});