【SEO対策】CSSの遅延読み込み処理

<!-- CSS 読み込みの遅延処理(SEO対策) -->
<noscript id="deferred-styles">
    <link href="/css/app1.css" rel="stylesheet">
    <link href="/css/app2.css" rel="stylesheet">
</noscript>

<script>
    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 = window.requestAnimationFrame || window.mozRequestAnimationFrame ||
        window.webkitRequestAnimationFrame || window.msRequestAnimationFrame;
    if (raf) raf(function() { window.setTimeout(loadDeferredStyles, 0); });
    else window.addEventListener('load', loadDeferredStyles);
</script>