JSFiddle - React, Tailwind, and code Playground

HTML

<select id="selection">
<option>Hello</option>
</select>
<span id="span">Hello</span>

CSS

#test {
  width: 50px;
}

JavaScript

function ApplyStyles(select, span) {
	var select = document.querySelector(select);
	var span = document.querySelector(span);
	var sheets = document.styleSheets;
  
	for(var i = 0; i < sheets.length; i++) {
		var rules = sheets[i].cssRules || sheets[i].rules;   
		for(var r = 0; r < rules.length; r++) {
			var rule = rules[r];
			var selectorText = rule.selectorText;
			if(document.querySelector(selectorText) == select){
        for(var l = 0; l < rule.style.length; l++){
        	span.style[rule.style[l]] = rule.style[rule.style[l]];
        }
			}
		}
	}
}

ApplyStyles("#selection", "#span");