JSFiddle - React, Tailwind, and code Playground

by brigand

HTML

<div id="subject">a</div>
<pre id="out"></pre>

CSS

div {
  background: #ffff00;
  line-height: 1.4;
}

JavaScript

{
	const { lineHeight, fontSize } = getComputedStyle(subject);
  const { height } = subject.getBoundingClientRect();
  
  out.textContent = `
height: ${height},
line-height: ${lineHeight}
1em is ${fontSize}
`
}