modernizr.details.js

// By @mathias, based on http://mths.be/axh
define([
    'modernizr/modernizr'
], function(){

    Modernizr.addTest('details', function() {
        var doc = document,
            el = doc.createElement('details'),
            fake,
            root,
            diff;
        if (!('open' in el)) { // return early if possible; thanks @aFarkas!
            return false;
        }
        root = doc.body || (function() {
            var de = doc.documentElement;
            fake = true;
            return de.insertBefore(doc.createElement('body'), de.firstElementChild || de.firstChild);
        }());
        el.innerHTML = '<summary>a</summary>b';
        el.style.display = 'block';
        root.appendChild(el);
        diff = el.offsetHeight;
        el.open = true;
        diff = diff != el.offsetHeight;
        root.removeChild(el);
        fake && root.parentNode.removeChild(root);
        return diff;
    });

});