title: Get element's resolved height CSS property value; recognize 100%
body: <blockquote>
  <p>The values returned by <code>getComputedStyle</code> are <strong>resolved values</strong>. These are usually the same as CSS 2.1’s computed values, but <em>for some older properties like <code>width</code>, <strong><code>height</code></strong>, or <code>padding</code></em>, they are instead the same as <strong>used values</strong>.</p>
  </blockquote>
  <p>-- <a href="https://developer.mozilla.org/en-US/docs/Web/API/Window/getComputedStyle#Notes" rel="nofollow noreferrer">MDN: window.getComputedStyle() notes</a></p>
  <p>So is it currently possible to get the <strong>resolved value</strong> of <code>height</code> as it was specified in stylesheet?</p>
  <p>I.e. know that some element's computed <code>..px</code> (= <strong>used</strong>) height was specified as <code>height: 100%;</code> in style sheet? (<strong><code>100%</code></strong> being the <strong>resolved</strong> value in question.)</p>
  <p>Is there some new specification regarding this problem in consideration?</p>
  <hr />
  <p>Edit 2020-08-17: see very similar question and excellent answer from 2012: <a href="https://stackoverflow.com/q/10970655/540955">Is there a cross-browser method of getting the used css values of all properties of all elements?</a>
  (Sadly, noting seem to ave changed since then.)</p>