// or  element, update the intersection rect.// Note:  and  cannot be clipped to a rect that's not also// the document rect, so no need to compute a new intersection.if (parent != document.body &&parent != document.documentElement &&parentComputedStyle.overflow != 'visible') {parentRect = getBoundingClientRect(parent);}}// If either of the above conditionals set a new parentRect,// calculate new intersection data.if (parentRect) {intersectionRect = computeRectIntersection(parentRect, intersectionRect);if (!intersectionRect) break;}parent = getParentNode(parent);}return intersectionRect;};/*** Returns the root rect after being expanded by the rootMargin value.* @return {Object} The expanded root rect.* @private*/IntersectionObserver.prototype._getRootRect = function() {var rootRect;if (this.root) {rootRect = getBoundingClientRect(this.root);} else {// Use / instead of window since scroll bars affect size.var html = document.documentElement;var body = document.body;rootRect = {top: 0,left: 0,right: html.clientWidth || body.clientWidth,width: html.clientWidth || body.clientWidth,bottom: html.clientHeight || body.clientHeight,height: html.clientHeight || body.clientHeight};}return this._expandRectByRootMargin(rootRect);};/*** Accepts a rect and expands it by the rootMargin value.* @param {Object} rect The rect object to expand.* @return {Object} The expanded rect.* @private*/IntersectionObserver.prototype._expandRectByRootMargin = function(rect) {var margins = this._rootMarginValues.map(function(margin, i) {return margin.unit == 'px' ? margin.value :margin.value * (i % 2 ? rect.width : rect.height) / 100;});var newRect = {top: rect.top - margins[0],right: rect.right + margins[1],bottom: rect.bottom + margins[2],left: rect.left - margins[3]};newRect.width = newRect.right - newRect.left;newRect.height = newRect.bottom - newRect.top;return newRect;};/*** Accepts an old and new entry and returns true if at least one of the* threshold values has been crossed.* @param {?IntersectionObserverEntry} oldEntry The previous entry for a*    particular target element or null if no previous entry exists.* @param {IntersectionObserverEntry} newEntry The current entry for a*    particular target element.* @return {boolean} Returns true if a any threshold has been crossed.* @private*/IntersectionObserver.prototype._hasCrossedThreshold =function(oldEntry, newEntry) {// To make comparing easier, an entry that has a ratio of 0// but does not actually intersect is given a value of -1var oldRatio = oldEntry && oldEntry.isIntersecting ?oldEntry.intersectionRatio || 0 : -1;var newRatio = newEntry.isIntersecting ?newEntry.intersectionRatio || 0 : -1;// Ignore unchanged ratiosif (oldRatio === newRatio) return;for (var i = 0; i = 0 && height >= 0) && {top: top,bottom: bottom,left: left,right: right,width: width,height: height};}/*** Shims the native getBoundingClientRect for compatibility with older IE.* @param {Element} el The element whose bounding rect to get.* @return {O