<!DOCTYPE html> <html> <body> <script> // Create a bunch of nested flex containers: var parentNode = document.body; var depth = 50; for (var i = 0; i < depth; i++) { var childNode = document.createElement("div"); childNode.style.display = "flex"; parentNode.appendChild(childNode); parentNode = childNode; } // Add some text in the innermost child: childNode.innerHTML = "Text"; // Force reflow: var height = document.body.children[0].offsetHeight; </script>