/*! https://mths.be/scrollingelement v1.5.2 by @diegoperini & @mathias | MIT license */ if (!('scrollingElement' in document)) (function() { function computeStyle(element) { if (window.getComputedStyle) { // Support Firefox < 4 which throws on a single parameter. return getComputedStyle(element, null); } // Support Internet Explorer < 9. return element.currentStyle; } function isBodyElement(element) { // The `instanceof` check gives the correct result for e.g. `body` in a // non-HTML namespace. if (window.HTMLBodyElement) { return element instanceof HTMLBodyElement; } // Fall back to a `tagName` check for old browsers. return /body/i.test(element.tagName); } function getNextBodyElement(frameset) { // We use this function to be correct per spec in case `document.body` is // a `frameset` but there exists a later `body`. Since `document.body` is // a `frameset`, we know the root is an `html`, and there was no `body` // before the `frameset`, so we just need to look at siblings after the // `frameset`. var current = frameset; while (current = current.nextSibling) { if (current.nodeType == 1 && isBodyElement(current)) { return current; } } // No `body` found. return null; } // Note: standards mode / quirks mode can be toggled at runtime via // `document.write`. var isCompliantCached; var isCompliant = function() { var isStandardsMode = /^CSS1/.test(document.compatMode); if (!isStandardsMode) { // In quirks mode, the result is equivalent to the non-compliant // standards mode behavior. return false; } if (isCompliantCached === void 0) { // When called for the first time, check whether the browser is // standard-compliant, and cache the result. var iframe = document.createElement('iframe'); iframe.style.height = '1px'; (document.body || document.documentElement || document).appendChild(iframe); var doc = iframe.contentWindow.document; doc.write('

x

'); doc.close(); isCompliantCached = doc.documentElement.scrollHeight > doc.body.scrollHeight; iframe.parentNode.removeChild(iframe); } return isCompliantCached; }; function isRendered(style) { return style.display != 'none' && !(style.visibility == 'collapse' && /^table-(.+-group|row|column)$/.test(style.display)); } function isScrollable(body) { // A `body` element is scrollable if `body` and `html` both have // non-`visible` overflow and are both being rendered. var bodyStyle = computeStyle(body); var htmlStyle = computeStyle(document.documentElement); return bodyStyle.overflow != 'visible' && htmlStyle.overflow != 'visible' && isRendered(bodyStyle) && isRendered(htmlStyle); } var scrollingElement = function() { if (isCompliant()) { return document.documentElement; } var body = document.body; // Note: `document.body` could be a `frameset` element, or `null`. // `tagName` is uppercase in HTML, but lowercase in XML. var isFrameset = body && !/body/i.test(body.tagName); body = isFrameset ? getNextBodyElement(body) : body; // If `body` is itself scrollable, it is not the `scrollingElement`. return body && isScrollable(body) ? null : body; }; if (Object.defineProperty) { // Support modern browsers that lack a native implementation. Object.defineProperty(document, 'scrollingElement', { 'get': scrollingElement }); } else if (document.__defineGetter__) { // Support Firefox ≤ 3.6.9, Safari ≤ 4.1.3. document.__defineGetter__('scrollingElement', scrollingElement); } else { // IE ≤ 4 lacks `attachEvent`, so it only gets this one assignment. IE ≤ 7 // gets it too, but the value is updated later (see `propertychange`). document.scrollingElement = scrollingElement(); document.attachEvent && document.attachEvent('onpropertychange', function() { // This is for IE ≤ 7 only. // A `propertychange` event fires when `` is parsed because // `document.activeElement` then changes. if (window.event.propertyName == 'activeElement') { document.scrollingElement = scrollingElement(); } }); } }());