<!DOCTYPE HTML> <!-- Any copyright is dedicated to the Public Domain. http://creativecommons.org/publicdomain/zero/1.0/ --> <html><head> <title>CSS Flexbox Test: dynamic change .left on abs.pos. item w. align-self:center</title> <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1405319"> <link rel="help" href="https://drafts.csswg.org/css-align-3/#propdef-align-self"> <link rel="match" href="flexbox-item-align-self-dynamic-pos-001-ref.html"> <style type="text/css"> html,body { color:black; background-color:white; font:16px/1 monospace; padding:0; margin:0; } .flexbox { display: flex; position: relative; height: 100px; } #item { background: grey; position: absolute; align-self: center; left: 10px; } </style> </head> <body> <div class="flexbox"> <div id="item">X</div> </div> <script> document.body.offsetLeft; var items = Array.prototype.slice.call(document.querySelectorAll('#item')); items.map(item => item.style.left = "20px"); document.body.offsetLeft; </script> </body> </html>