Use setTimeout and querySelectorAll for IE11-compatible prefetch fallback

stylesheet-prefetch-fallback-2.js

function loadStylesheets() {

    // Give it a few seconds so that the browsers that support prefetch + onload have a chance to load the styles.
    // After a few seconds though, we should double-check to make sure the styles loaded.
    setTimeout(function () {
        var prefetchLinks = document.querySelectorAll('link[rel=prefetch]');

        // The onload attribute should be switching out the rel value from prefetch to stylesheet.
        // If that hasn't happened, then we'll need to manually intervene.
        if (0 === prefetchLinks.length) {
            return false;
        }

        for (i = 0; i < prefetchLinks.length; i++) {
            var prefetchLink = prefetchLinks[i];

            var linkType = prefetchLink.getAttribute('as');
            var linkOnload = prefetchLink.getAttribute('onload');

            if ('style' === linkType) {
                // Update the link's rel attribute and clear out "as".
                // This change should be reflected in the inspector in IE11 and Edge.
                prefetchLink.setAttribute('rel', 'stylesheet');
                prefetchLink.removeAttribute('as');
            }
            if ('' !== linkOnload) {
                // Remove the onload attribute.
                // This change should be reflected in the inspector in IE11 and Edge.
                prefetchLink.removeAttribute('onload');
            }
        }
    }, 3000);
}

window.addEventListener('load', loadStylesheets, false);