optimizeCSSLoading

loadStyles.js

var loadDeferredStyles = function() {
    var addStylesNode = document.getElementById("deferred-styles");
    var replacement = document.createElement("div");
    replacement.innerHTML = addStylesNode.textContent;
    document.body.appendChild(replacement)
    addStylesNode.parentElement.removeChild(addStylesNode);
};
var raf = requestAnimationFrame || mozRequestAnimationFrame ||
    webkitRequestAnimationFrame || msRequestAnimationFrame;
if (raf) raf(function() { window.setTimeout(loadDeferredStyles, 0); });
else window.addEventListener('load', loadDeferredStyles);

style-part.html

<!-- include after footer -->
<noscript id="deferred-styles">
    <link href="{{ asset('css/app.css') }}" rel="stylesheet">
    <link href="{{ asset('css/additional.css') }}" rel="stylesheet">
</noscript>