Add upstream

wp-content/plugins/jetpack/modules/lazy-images/js/lazy-images.js

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+/* globals IntersectionObserver, jQuery */
+
+var jetpackLazyImagesModule = function( $ ) {
+	var images,
+		config = {
+			// If the image gets within 200px in the Y axis, start the download.
+			rootMargin: '200px 0px',
+			threshold: 0.01
+		},
+		imageCount = 0,
+		observer,
+		image,
+		i;
+
+	$( document ).ready( function() {
+		lazy_load_init();
+
+		// Lazy load images that are brought in from Infinite Scroll
+		$( 'body' ).bind( 'post-load', lazy_load_init );
+
+		// Add event to provide optional compatibility for other code.
+		$( 'body' ).bind( 'jetpack-lazy-images-load', lazy_load_init );
+	} );
+
+	function lazy_load_init() {
+		images = document.querySelectorAll( 'img.jetpack-lazy-image:not(.jetpack-lazy-image--handled)' );
+		imageCount = images.length;
+
+		// If initialized, then disconnect the observer
+		if ( observer ) {
+			observer.disconnect();
+		}
+
+		// If we don't have support for intersection observer, loads the images immediately
+		if ( ! ( 'IntersectionObserver' in window ) ) {
+			loadImagesImmediately( images );
+		} else {
+			// It is supported, load the images
+			observer = new IntersectionObserver( onIntersection, config );
+
+			// foreach() is not supported in IE
+			for ( i = 0; i < images.length; i++ ) {
+				image = images[ i ];
+				if ( image.getAttribute( 'data-lazy-loaded' ) ) {
+					continue;
+				}
+
+				observer.observe( image );
+			}
+		}
+	}
+
+	/**
+	 * Load all of the images immediately
+	 * @param {NodeListOf<Element>} immediateImages List of lazy-loaded images to load immediately.
+	 */
+	function loadImagesImmediately( immediateImages ) {
+		var i;
+
+		// foreach() is not supported in IE
+		for ( i = 0; i < immediateImages.length; i++ ) {
+			var image = immediateImages[ i ];
+			applyImage( image );
+		}
+	}
+
+	/**
+	 * On intersection
+	 * @param {array} entries List of elements being observed.
+	 */
+	function onIntersection( entries ) {
+		var i;
+
+		// Disconnect if we've already loaded all of the images
+		if ( imageCount === 0 ) {
+			observer.disconnect();
+		}
+
+		// Loop through the entries
+		for ( i = 0; i < entries.length; i++ ) {
+			var entry = entries[ i ];
+
+			// Are we in viewport?
+			if ( entry.intersectionRatio > 0 ) {
+				imageCount--;
+
+				// Stop watching and load the image
+				observer.unobserve( entry.target );
+				applyImage( entry.target );
+			}
+		}
+	}
+
+	/**
+	 * Apply the image
+	 * @param {object} image The image object.
+	 */
+	function applyImage( image ) {
+		var theImage = $( image ),
+			srcset,
+			sizes,
+			theClone;
+
+		if ( ! theImage.length ) {
+			return;
+		}
+
+		srcset = theImage.attr( 'data-lazy-srcset' );
+		sizes = theImage.attr( 'data-lazy-sizes' );
+		theClone = theImage.clone(true);
+
+		// Remove lazy attributes from the clone.
+		theClone.removeAttr( 'data-lazy-srcset' ),
+		theClone.removeAttr( 'data-lazy-sizes' );
+		theClone.removeAttr( 'data-lazy-src' );
+
+		// Add the attributes we want on the finished image.
+		theClone.addClass( 'jetpack-lazy-image--handled' );
+		theClone.attr( 'data-lazy-loaded', 1 );
+		if ( ! srcset ) {
+			theClone.removeAttr( 'srcset' );
+		} else {
+			theClone.attr( 'srcset', srcset );
+		}
+		if ( sizes ) {
+			theClone.attr( 'sizes', sizes );
+		}
+
+		theImage.replaceWith( theClone );
+
+		// Fire an event so that third-party code can perform actions after an image is loaded.
+		theClone.trigger( 'jetpack-lazy-loaded-image' );
+	}
+};
+
+/**
+ * The following is an Intersection observer polyfill which is licensed under
+ * the W3C SOFTWARE AND DOCUMENT NOTICE AND LICENSE and can be found at:
+ * https://github.com/w3c/IntersectionObserver/tree/master/polyfill
+ */
+
+/* jshint ignore:start */
+/**
+ * Copyright 2016 Google Inc. All Rights Reserved.
+ *
+ * Licensed under the W3C SOFTWARE AND DOCUMENT NOTICE AND LICENSE.
+ *
+ *  https://www.w3.org/Consortium/Legal/2015/copyright-software-and-document
+ *
+ */
+
+(function(window, document) {
+	'use strict';
+
+
+	// Exits early if all IntersectionObserver and IntersectionObserverEntry
+	// features are natively supported.
+	if ('IntersectionObserver' in window &&
+		'IntersectionObserverEntry' in window &&
+		'intersectionRatio' in window.IntersectionObserverEntry.prototype) {
+
+	  // Minimal polyfill for Edge 15's lack of `isIntersecting`
+	  // See: https://github.com/w3c/IntersectionObserver/issues/211
+	  if (!('isIntersecting' in window.IntersectionObserverEntry.prototype)) {
+		Object.defineProperty(window.IntersectionObserverEntry.prototype,
+		  'isIntersecting', {
+		  get: function () {
+			return this.intersectionRatio > 0;
+		  }
+		});
+	  }
+	  return;
+	}
+
+
+	/**
+	 * An IntersectionObserver registry. This registry exists to hold a strong
+	 * reference to IntersectionObserver instances currently observering a target
+	 * element. Without this registry, instances without another reference may be
+	 * garbage collected.
+	 */
+	var registry = [];
+
+
+	/**
+	 * Creates the global IntersectionObserverEntry constructor.
+	 * https://w3c.github.io/IntersectionObserver/#intersection-observer-entry
+	 * @param {Object} entry A dictionary of instance properties.
+	 * @constructor
+	 */
+	function IntersectionObserverEntry(entry) {
+	  this.time = entry.time;
+	  this.target = entry.target;
+	  this.rootBounds = entry.rootBounds;
+	  this.boundingClientRect = entry.boundingClientRect;
+	  this.intersectionRect = entry.intersectionRect || getEmptyRect();
+	  this.isIntersecting = !!entry.intersectionRect;
+
+	  // Calculates the intersection ratio.
+	  var targetRect = this.boundingClientRect;
+	  var targetArea = targetRect.width * targetRect.height;
+	  var intersectionRect = this.intersectionRect;
+	  var intersectionArea = intersectionRect.width * intersectionRect.height;
+
+	  // Sets intersection ratio.
+	  if (targetArea) {
+		this.intersectionRatio = intersectionArea / targetArea;
+	  } else {
+		// If area is zero and is intersecting, sets to 1, otherwise to 0
+		this.intersectionRatio = this.isIntersecting ? 1 : 0;
+	  }
+	}
+
+
+	/**
+	 * Creates the global IntersectionObserver constructor.
+	 * https://w3c.github.io/IntersectionObserver/#intersection-observer-interface
+	 * @param {Function} callback The function to be invoked after intersection
+	 *     changes have queued. The function is not invoked if the queue has
+	 *     been emptied by calling the `takeRecords` method.
+	 * @param {Object=} opt_options Optional configuration options.
+	 * @constructor
+	 */
+	function IntersectionObserver(callback, opt_options) {
+
+	  var options = opt_options || {};
+
+	  if (typeof callback != 'function') {
+		throw new Error('callback must be a function');
+	  }
+
+	  if (options.root && options.root.nodeType != 1) {
+		throw new Error('root must be an Element');
+	  }
+
+	  // Binds and throttles `this._checkForIntersections`.
+	  this._checkForIntersections = throttle(
+		  this._checkForIntersections.bind(this), this.THROTTLE_TIMEOUT);
+
+	  // Private properties.
+	  this._callback = callback;
+	  this._observationTargets = [];
+	  this._queuedEntries = [];
+	  this._rootMarginValues = this._parseRootMargin(options.rootMargin);
+
+	  // Public properties.
+	  this.thresholds = this._initThresholds(options.threshold);
+	  this.root = options.root || null;
+	  this.rootMargin = this._rootMarginValues.map(function(margin) {
+		return margin.value + margin.unit;
+	  }).join(' ');
+	}
+
+
+	/**
+	 * The minimum interval within which the document will be checked for
+	 * intersection changes.
+	 */
+	IntersectionObserver.prototype.THROTTLE_TIMEOUT = 100;
+
+
+	/**
+	 * The frequency in which the polyfill polls for intersection changes.
+	 * this can be updated on a per instance basis and must be set prior to
+	 * calling `observe` on the first target.
+	 */
+	IntersectionObserver.prototype.POLL_INTERVAL = null;
+
+	/**
+	 * Use a mutation observer on the root element
+	 * to detect intersection changes.
+	 */
+	IntersectionObserver.prototype.USE_MUTATION_OBSERVER = true;
+
+
+	/**
+	 * Starts observing a target element for intersection changes based on
+	 * the thresholds values.
+	 * @param {Element} target The DOM element to observe.
+	 */
+	IntersectionObserver.prototype.observe = function(target) {
+	  var isTargetAlreadyObserved = this._observationTargets.some(function(item) {
+		return item.element == target;
+	  });
+
+	  if (isTargetAlreadyObserved) {
+		return;
+	  }
+
+	  if (!(target && target.nodeType == 1)) {
+		throw new Error('target must be an Element');
+	  }
+
+	  this._registerInstance();
+	  this._observationTargets.push({element: target, entry: null});
+	  this._monitorIntersections();
+	  this._checkForIntersections();
+	};
+
+
+	/**
+	 * Stops observing a target element for intersection changes.
+	 * @param {Element} target The DOM element to observe.
+	 */
+	IntersectionObserver.prototype.unobserve = function(target) {
+	  this._observationTargets =
+		  this._observationTargets.filter(function(item) {
+
+		return item.element != target;
+	  });
+	  if (!this._observationTargets.length) {
+		this._unmonitorIntersections();
+		this._unregisterInstance();
+	  }
+	};
+
+
+	/**
+	 * Stops observing all target elements for intersection changes.
+	 */
+	IntersectionObserver.prototype.disconnect = function() {
+	  this._observationTargets = [];
+	  this._unmonitorIntersections();
+	  this._unregisterInstance();
+	};
+
+
+	/**
+	 * Returns any queue entries that have not yet been reported to the
+	 * callback and clears the queue. This can be used in conjunction with the
+	 * callback to obtain the absolute most up-to-date intersection information.
+	 * @return {Array} The currently queued entries.
+	 */
+	IntersectionObserver.prototype.takeRecords = function() {
+	  var records = this._queuedEntries.slice();
+	  this._queuedEntries = [];
+	  return records;
+	};
+
+
+	/**
+	 * Accepts the threshold value from the user configuration object and
+	 * returns a sorted array of unique threshold values. If a value is not
+	 * between 0 and 1 and error is thrown.
+	 * @private
+	 * @param {Array|number=} opt_threshold An optional threshold value or
+	 *     a list of threshold values, defaulting to [0].
+	 * @return {Array} A sorted list of unique and valid threshold values.
+	 */
+	IntersectionObserver.prototype._initThresholds = function(opt_threshold) {
+	  var threshold = opt_threshold || [0];
+	  if (!Array.isArray(threshold)) threshold = [threshold];
+
+	  return threshold.sort().filter(function(t, i, a) {
+		if (typeof t != 'number' || isNaN(t) || t < 0 || t > 1) {
+		  throw new Error('threshold must be a number between 0 and 1 inclusively');
+		}
+		return t !== a[i - 1];
+	  });
+	};
+
+
+	/**
+	 * Accepts the rootMargin value from the user configuration object
+	 * and returns an array of the four margin values as an object containing
+	 * the value and unit properties. If any of the values are not properly
+	 * formatted or use a unit other than px or %, and error is thrown.
+	 * @private
+	 * @param {string=} opt_rootMargin An optional rootMargin value,
+	 *     defaulting to '0px'.
+	 * @return {Array<Object>} An array of margin objects with the keys
+	 *     value and unit.
+	 */
+	IntersectionObserver.prototype._parseRootMargin = function(opt_rootMargin) {
+	  var marginString = opt_rootMargin || '0px';
+	  var margins = marginString.split(/\s+/).map(function(margin) {
+		var parts = /^(-?\d*\.?\d+)(px|%)$/.exec(margin);
+		if (!parts) {
+		  throw new Error('rootMargin must be specified in pixels or percent');
+		}
+		return {value: parseFloat(parts[1]), unit: parts[2]};
+	  });
+
+	  // Handles shorthand.
+	  margins[1] = margins[1] || margins[0];
+	  margins[2] = margins[2] || margins[0];
+	  margins[3] = margins[3] || margins[1];
+
+	  return margins;
+	};
+
+
+	/**
+	 * Starts polling for intersection changes if the polling is not already
+	 * happening, and if the page's visibilty state is visible.
+	 * @private
+	 */
+	IntersectionObserver.prototype._monitorIntersections = function() {
+	  if (!this._monitoringIntersections) {
+		this._monitoringIntersections = true;
+
+		// If a poll interval is set, use polling instead of listening to
+		// resize and scroll events or DOM mutations.
+		if (this.POLL_INTERVAL) {
+		  this._monitoringInterval = setInterval(
+			  this._checkForIntersections, this.POLL_INTERVAL);
+		}
+		else {
+		  addEvent(window, 'resize', this._checkForIntersections, true);
+		  addEvent(document, 'scroll', this._checkForIntersections, true);
+
+		  if (this.USE_MUTATION_OBSERVER && 'MutationObserver' in window) {
+			this._domObserver = new MutationObserver(this._checkForIntersections);
+			this._domObserver.observe(document, {
+			  attributes: true,
+			  childList: true,
+			  characterData: true,
+			  subtree: true
+			});
+		  }
+		}
+	  }
+	};
+
+
+	/**
+	 * Stops polling for intersection changes.
+	 * @private
+	 */
+	IntersectionObserver.prototype._unmonitorIntersections = function() {
+	  if (this._monitoringIntersections) {
+		this._monitoringIntersections = false;
+
+		clearInterval(this._monitoringInterval);
+		this._monitoringInterval = null;
+
+		removeEvent(window, 'resize', this._checkForIntersections, true);
+		removeEvent(document, 'scroll', this._checkForIntersections, true);
+
+		if (this._domObserver) {
+		  this._domObserver.disconnect();
+		  this._domObserver = null;
+		}
+	  }
+	};
+
+
+	/**
+	 * Scans each observation target for intersection changes and adds them
+	 * to the internal entries queue. If new entries are found, it
+	 * schedules the callback to be invoked.
+	 * @private
+	 */
+	IntersectionObserver.prototype._checkForIntersections = function() {
+	  var rootIsInDom = this._rootIsInDom();
+	  var rootRect = rootIsInDom ? this._getRootRect() : getEmptyRect();
+
+	  this._observationTargets.forEach(function(item) {
+		var target = item.element;
+		var targetRect = getBoundingClientRect(target);
+		var rootContainsTarget = this._rootContainsTarget(target);
+		var oldEntry = item.entry;
+		var intersectionRect = rootIsInDom && rootContainsTarget &&
+			this._computeTargetAndRootIntersection(target, rootRect);
+
+		var newEntry = item.entry = new IntersectionObserverEntry({
+		  time: now(),
+		  target: target,
+		  boundingClientRect: targetRect,
+		  rootBounds: rootRect,
+		  intersectionRect: intersectionRect
+		});
+
+		if (!oldEntry) {
+		  this._queuedEntries.push(newEntry);
+		} else if (rootIsInDom && rootContainsTarget) {
+		  // If the new entry intersection ratio has crossed any of the
+		  // thresholds, add a new entry.
+		  if (this._hasCrossedThreshold(oldEntry, newEntry)) {
+			this._queuedEntries.push(newEntry);
+		  }
+		} else {
+		  // If the root is not in the DOM or target is not contained within
+		  // root but the previous entry for this target had an intersection,
+		  // add a new record indicating removal.
+		  if (oldEntry && oldEntry.isIntersecting) {
+			this._queuedEntries.push(newEntry);
+		  }
+		}
+	  }, this);
+
+	  if (this._queuedEntries.length) {
+		this._callback(this.takeRecords(), this);
+	  }
+	};
+
+
+	/**
+	 * Accepts a target and root rect computes the intersection between then
+	 * following the algorithm in the spec.
+	 * TODO(philipwalton): at this time clip-path is not considered.
+	 * https://w3c.github.io/IntersectionObserver/#calculate-intersection-rect-algo
+	 * @param {Element} target The target DOM element
+	 * @param {Object} rootRect The bounding rect of the root after being
+	 *     expanded by the rootMargin value.
+	 * @return {?Object} The final intersection rect object or undefined if no
+	 *     intersection is found.
+	 * @private
+	 */
+	IntersectionObserver.prototype._computeTargetAndRootIntersection =
+		function(target, rootRect) {
+
+	  // If the element isn't displayed, an intersection can't happen.
+	  if (window.getComputedStyle(target).display == 'none') return;
+
+	  var targetRect = getBoundingClientRect(target);
+	  var intersectionRect = targetRect;
+	  var parent = getParentNode(target);
+	  var atRoot = false;
+
+	  while (!atRoot) {
+		var parentRect = null;
+		var parentComputedStyle = parent.nodeType == 1 ?
+			window.getComputedStyle(parent) : {};
+
+		// If the parent isn't displayed, an intersection can't happen.
+		if (parentComputedStyle.display == 'none') return;
+
+		if (parent == this.root || parent == document) {
+		  atRoot = true;
+		  parentRect = rootRect;
+		} else {
+		  // If the element has a non-visible overflow, and it's not the <body>
+		  // or <html> element, update the intersection rect.
+		  // Note: <body> and <html> 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 <html>/<body> 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 -1
+	  var oldRatio = oldEntry && oldEntry.isIntersecting ?
+		  oldEntry.intersectionRatio || 0 : -1;
+	  var newRatio = newEntry.isIntersecting ?
+		  newEntry.intersectionRatio || 0 : -1;
+
+	  // Ignore unchanged ratios
+	  if (oldRatio === newRatio) return;
+
+	  for (var i = 0; i < this.thresholds.length; i++) {
+		var threshold = this.thresholds[i];
+
+		// Return true if an entry matches a threshold or if the new ratio
+		// and the old ratio are on the opposite sides of a threshold.
+		if (threshold == oldRatio || threshold == newRatio ||
+			threshold < oldRatio !== threshold < newRatio) {
+		  return true;
+		}
+	  }
+	};
+
+
+	/**
+	 * Returns whether or not the root element is an element and is in the DOM.
+	 * @return {boolean} True if the root element is an element and is in the DOM.
+	 * @private
+	 */
+	IntersectionObserver.prototype._rootIsInDom = function() {
+	  return !this.root || containsDeep(document, this.root);
+	};
+
+
+	/**
+	 * Returns whether or not the target element is a child of root.
+	 * @param {Element} target The target element to check.
+	 * @return {boolean} True if the target element is a child of root.
+	 * @private
+	 */
+	IntersectionObserver.prototype._rootContainsTarget = function(target) {
+	  return containsDeep(this.root || document, target);
+	};
+
+
+	/**
+	 * Adds the instance to the global IntersectionObserver registry if it isn't
+	 * already present.
+	 * @private
+	 */
+	IntersectionObserver.prototype._registerInstance = function() {
+	  if (registry.indexOf(this) < 0) {
+		registry.push(this);
+	  }
+	};
+
+
+	/**
+	 * Removes the instance from the global IntersectionObserver registry.
+	 * @private
+	 */
+	IntersectionObserver.prototype._unregisterInstance = function() {
+	  var index = registry.indexOf(this);
+	  if (index != -1) registry.splice(index, 1);
+	};
+
+
+	/**
+	 * Returns the result of the performance.now() method or null in browsers
+	 * that don't support the API.
+	 * @return {number} The elapsed time since the page was requested.
+	 */
+	function now() {
+	  return window.performance && performance.now && performance.now();
+	}
+
+
+	/**
+	 * Throttles a function and delays its executiong, so it's only called at most
+	 * once within a given time period.
+	 * @param {Function} fn The function to throttle.
+	 * @param {number} timeout The amount of time that must pass before the
+	 *     function can be called again.
+	 * @return {Function} The throttled function.
+	 */
+	function throttle(fn, timeout) {
+	  var timer = null;
+	  return function () {
+		if (!timer) {
+		  timer = setTimeout(function() {
+			fn();
+			timer = null;
+		  }, timeout);
+		}
+	  };
+	}
+
+
+	/**
+	 * Adds an event handler to a DOM node ensuring cross-browser compatibility.
+	 * @param {Node} node The DOM node to add the event handler to.
+	 * @param {string} event The event name.
+	 * @param {Function} fn The event handler to add.
+	 * @param {boolean} opt_useCapture Optionally adds the even to the capture
+	 *     phase. Note: this only works in modern browsers.
+	 */
+	function addEvent(node, event, fn, opt_useCapture) {
+	  if (typeof node.addEventListener == 'function') {
+		node.addEventListener(event, fn, opt_useCapture || false);
+	  }
+	  else if (typeof node.attachEvent == 'function') {
+		node.attachEvent('on' + event, fn);
+	  }
+	}
+
+
+	/**
+	 * Removes a previously added event handler from a DOM node.
+	 * @param {Node} node The DOM node to remove the event handler from.
+	 * @param {string} event The event name.
+	 * @param {Function} fn The event handler to remove.
+	 * @param {boolean} opt_useCapture If the event handler was added with this
+	 *     flag set to true, it should be set to true here in order to remove it.
+	 */
+	function removeEvent(node, event, fn, opt_useCapture) {
+	  if (typeof node.removeEventListener == 'function') {
+		node.removeEventListener(event, fn, opt_useCapture || false);
+	  }
+	  else if (typeof node.detatchEvent == 'function') {
+		node.detatchEvent('on' + event, fn);
+	  }
+	}
+
+
+	/**
+	 * Returns the intersection between two rect objects.
+	 * @param {Object} rect1 The first rect.
+	 * @param {Object} rect2 The second rect.
+	 * @return {?Object} The intersection rect or undefined if no intersection
+	 *     is found.
+	 */
+	function computeRectIntersection(rect1, rect2) {
+	  var top = Math.max(rect1.top, rect2.top);
+	  var bottom = Math.min(rect1.bottom, rect2.bottom);
+	  var left = Math.max(rect1.left, rect2.left);
+	  var right = Math.min(rect1.right, rect2.right);
+	  var width = right - left;
+	  var height = bottom - top;
+
+	  return (width >= 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 {Object} The (possibly shimmed) rect of the element.
+	 */
+	function getBoundingClientRect(el) {
+	  var rect;
+
+	  try {
+		rect = el.getBoundingClientRect();
+	  } catch (err) {
+		// Ignore Windows 7 IE11 "Unspecified error"
+		// https://github.com/w3c/IntersectionObserver/pull/205
+	  }
+
+	  if (!rect) return getEmptyRect();
+
+	  // Older IE
+	  if (!(rect.width && rect.height)) {
+		rect = {
+		  top: rect.top,
+		  right: rect.right,
+		  bottom: rect.bottom,
+		  left: rect.left,
+		  width: rect.right - rect.left,
+		  height: rect.bottom - rect.top
+		};
+	  }
+	  return rect;
+	}
+
+
+	/**
+	 * Returns an empty rect object. An empty rect is returned when an element
+	 * is not in the DOM.
+	 * @return {Object} The empty rect.
+	 */
+	function getEmptyRect() {
+	  return {
+		top: 0,
+		bottom: 0,
+		left: 0,
+		right: 0,
+		width: 0,
+		height: 0
+	  };
+	}
+
+	/**
+	 * Checks to see if a parent element contains a child elemnt (including inside
+	 * shadow DOM).
+	 * @param {Node} parent The parent element.
+	 * @param {Node} child The child element.
+	 * @return {boolean} True if the parent node contains the child node.
+	 */
+	function containsDeep(parent, child) {
+	  var node = child;
+	  while (node) {
+		if (node == parent) return true;
+
+		node = getParentNode(node);
+	  }
+	  return false;
+	}
+
+
+	/**
+	 * Gets the parent node of an element or its host element if the parent node
+	 * is a shadow root.
+	 * @param {Node} node The node whose parent to get.
+	 * @return {Node|null} The parent node or null if no parent exists.
+	 */
+	function getParentNode(node) {
+	  var parent = node.parentNode;
+
+	  if (parent && parent.nodeType == 11 && parent.host) {
+		// If the parent is a shadow root, return the host element.
+		return parent.host;
+	  }
+	  return parent;
+	}
+
+
+	// Exposes the constructors globally.
+	window.IntersectionObserver = IntersectionObserver;
+	window.IntersectionObserverEntry = IntersectionObserverEntry;
+
+	}(window, document));
+/* jshint ignore:end */
+
+// Let's kick things off now
+jetpackLazyImagesModule( jQuery );

wp-content/plugins/jetpack/modules/lazy-images/lazy-images.php

@@ -0,0 +1,355 @@
+<?php
+
+use Automattic\Jetpack\Assets;
+
+class Jetpack_Lazy_Images {
+	private static $__instance = null;
+
+	/**
+	 * Singleton implementation
+	 *
+	 * @return object
+	 */
+	public static function instance() {
+		if ( is_null( self::$__instance ) ) {
+			self::$__instance = new Jetpack_Lazy_Images();
+		}
+
+		return self::$__instance;
+	}
+
+	/**
+	 * Registers actions
+	 */
+	private function __construct() {
+		if ( is_admin() ) {
+			return;
+		}
+
+		/**
+		 * Whether the lazy-images module should load.
+		 *
+		 * This filter is not prefixed with jetpack_ to provide a smoother migration
+		 * process from the WordPress Lazy Load plugin.
+		 *
+		 * @module lazy-images
+		 *
+		 * @since 5.6.0
+		 *
+		 * @param bool true Whether lazy image loading should occur.
+		 */
+		if ( ! apply_filters( 'lazyload_is_enabled', true ) ) {
+			return;
+		}
+
+		if ( Jetpack_AMP_Support::is_amp_request() ) {
+			return;
+		}
+
+		add_action( 'wp_head', array( $this, 'setup_filters' ), 9999 ); // we don't really want to modify anything in <head> since it's mostly all metadata
+		add_action( 'wp_enqueue_scripts', array( $this, 'enqueue_assets' ) );
+
+		// Do not lazy load avatar in admin bar
+		add_action( 'admin_bar_menu', array( $this, 'remove_filters' ), 0 );
+
+		add_filter( 'wp_kses_allowed_html', array( $this, 'allow_lazy_attributes' ) );
+		add_action( 'wp_head', array( $this, 'add_nojs_fallback' ) );
+	}
+
+	public function setup_filters() {
+		add_filter( 'the_content', array( $this, 'add_image_placeholders' ), PHP_INT_MAX ); // run this later, so other content filters have run, including image_add_wh on WP.com
+		add_filter( 'post_thumbnail_html', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
+		add_filter( 'get_avatar', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
+		add_filter( 'widget_text', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
+		add_filter( 'get_image_tag', array( $this, 'add_image_placeholders' ), PHP_INT_MAX);
+		add_filter( 'wp_get_attachment_image_attributes', array( __CLASS__, 'process_image_attributes' ), PHP_INT_MAX );
+	}
+
+	public function remove_filters() {
+		remove_filter( 'the_content', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
+		remove_filter( 'post_thumbnail_html', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
+		remove_filter( 'get_avatar', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
+		remove_filter( 'widget_text', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
+		remove_filter( 'get_image_tag', array( $this, 'add_image_placeholders' ), PHP_INT_MAX);
+		remove_filter( 'wp_get_attachment_image_attributes', array( __CLASS__, 'process_image_attributes' ), PHP_INT_MAX );
+	}
+
+	/**
+	 * Ensure that our lazy image attributes are not filtered out of image tags.
+	 *
+	 * @param array $allowed_tags The allowed tags and their attributes.
+	 * @return array
+	 */
+	public function allow_lazy_attributes( $allowed_tags ) {
+		if ( ! isset( $allowed_tags['img'] ) ) {
+			return $allowed_tags;
+		}
+
+		// But, if images are allowed, ensure that our attributes are allowed!
+		$img_attributes = array_merge( $allowed_tags['img'], array(
+			'data-lazy-src' => 1,
+			'data-lazy-srcset' => 1,
+			'data-lazy-sizes' => 1,
+		) );
+
+		$allowed_tags['img'] = $img_attributes;
+
+		return $allowed_tags;
+	}
+
+	public function add_image_placeholders( $content ) {
+		// Don't lazyload for feeds, previews
+		if ( is_feed() || is_preview() ) {
+			return $content;
+		}
+
+		// Don't lazy-load if the content has already been run through previously
+		if ( false !== strpos( $content, 'data-lazy-src' ) ) {
+			return $content;
+		}
+
+		// This is a pretty simple regex, but it works
+		$content = preg_replace_callback( '#<(img)([^>]+?)(>(.*?)</\\1>|[\/]?>)#si', array( __CLASS__, 'process_image' ), $content );
+
+		return $content;
+	}
+
+	/**
+	 * Returns true when a given string of classes contains a class signifying lazy images
+	 * should not process the image.
+	 *
+	 * @since 5.9.0
+	 *
+	 * @param string $classes A string of space-separated classes.
+	 * @return bool
+	 */
+	public static function should_skip_image_with_blacklisted_class( $classes ) {
+		$blacklisted_classes = array(
+			'skip-lazy',
+			'gazette-featured-content-thumbnail',
+		);
+
+		/**
+		 * Allow plugins and themes to tell lazy images to skip an image with a given class.
+		 *
+		 * @module lazy-images
+		 *
+		 * @since 5.9.0
+		 *
+		 * @param array An array of strings where each string is a class.
+		 */
+		$blacklisted_classes = apply_filters( 'jetpack_lazy_images_blacklisted_classes', $blacklisted_classes );
+
+		if ( ! is_array( $blacklisted_classes ) || empty( $blacklisted_classes ) ) {
+			return false;
+		}
+
+		foreach ( $blacklisted_classes as $class ) {
+			if ( false !== strpos( $classes, $class ) ) {
+				return true;
+			}
+		}
+
+		return false;
+	}
+
+	/**
+	 * Processes images in content by acting as the preg_replace_callback
+	 *
+	 * @since 5.6.0
+	 *
+	 * @param array $matches
+	 *
+	 * @return string The image with updated lazy attributes
+	 */
+	static function process_image( $matches ) {
+		$old_attributes_str       = $matches[2];
+		$old_attributes_kses_hair = wp_kses_hair( $old_attributes_str, wp_allowed_protocols() );
+
+		if ( empty( $old_attributes_kses_hair['src'] ) ) {
+			return $matches[0];
+		}
+
+		$old_attributes = self::flatten_kses_hair_data( $old_attributes_kses_hair );
+
+		// If we didn't add lazy attributes, just return the original image source.
+		if ( ! empty( $old_attributes['class'] ) && false !== strpos( $old_attributes['class'], 'jetpack-lazy-image' ) ) {
+			return $matches[0];
+		}
+
+		$new_attributes     = self::process_image_attributes( $old_attributes );
+		$new_attributes_str = self::build_attributes_string( $new_attributes );
+
+		return sprintf( '<img %1$s><noscript>%2$s</noscript>', $new_attributes_str, $matches[0] );
+	}
+
+	/**
+	 * Given an array of image attributes, updates the `src`, `srcset`, and `sizes` attributes so
+	 * that they load lazily.
+	 *
+	 * @since 5.7.0
+	 *
+	 * @param array $attributes
+	 *
+	 * @return array The updated image attributes array with lazy load attributes
+	 */
+	static function process_image_attributes( $attributes ) {
+		if ( empty( $attributes['src'] ) ) {
+			return $attributes;
+		}
+
+		if ( ! empty( $attributes['class'] ) && self::should_skip_image_with_blacklisted_class( $attributes['class'] ) ) {
+			return $attributes;
+		}
+
+		/**
+		 * Allow plugins and themes to conditionally skip processing an image via its attributes.
+		 *
+		 * @module-lazy-images
+		 *
+		 * @deprecated 6.5.0 Use jetpack_lazy_images_skip_image_with_attributes instead.
+		 *
+		 * @since 5.9.0
+		 *
+		 * @param bool  Default to not skip processing the current image.
+		 * @param array An array of attributes via wp_kses_hair() for the current image.
+		 */
+		if ( apply_filters( 'jetpack_lazy_images_skip_image_with_atttributes', false, $attributes ) ) {
+			return $attributes;
+		}
+
+		/**
+		 * Allow plugins and themes to conditionally skip processing an image via its attributes.
+		 *
+		 * @module-lazy-images
+		 *
+		 * @since 6.5.0 Filter name was updated from jetpack_lazy_images_skip_image_with_atttributes to correct typo.
+		 * @since 5.9.0
+		 *
+		 * @param bool  Default to not skip processing the current image.
+		 * @param array An array of attributes via wp_kses_hair() for the current image.
+		 */
+		if ( apply_filters( 'jetpack_lazy_images_skip_image_with_attributes', false, $attributes ) ) {
+			return $attributes;
+		}
+
+		$old_attributes = $attributes;
+
+		// Stash srcset and sizes in data attributes.
+		foreach ( array( 'srcset', 'sizes' ) as $attribute ) {
+			if ( isset( $old_attributes[ $attribute ] ) ) {
+				$attributes[ "data-lazy-$attribute" ] = $old_attributes[ $attribute ];
+				unset( $attributes[ $attribute ] );
+			}
+		}
+
+		// We set this, adding the query arg so that it doesn't exactly equal the src attribute, so that photon JavaScript
+		// will hold off on processing this image.
+		$attributes['data-lazy-src'] = esc_url_raw( add_query_arg( 'is-pending-load', true, $attributes['src'] ) );
+
+		$attributes['srcset'] = self::get_placeholder_image();
+		$attributes['class']  = sprintf(
+			'%s jetpack-lazy-image',
+			empty( $old_attributes['class'] )
+				? ''
+				: $old_attributes['class']
+		);
+
+		/**
+		 * Allow plugins and themes to override the attributes on the image before the content is updated.
+		 *
+		 * One potential use of this filter is for themes that set `height:auto` on the `img` tag.
+		 * With this filter, the theme could get the width and height attributes from the
+		 * $attributes array and then add a style tag that sets those values as well, which could
+		 * minimize reflow as images load.
+		 *
+		 * @module lazy-images
+		 *
+		 * @since 5.6.0
+		 *
+		 * @param array An array containing the attributes for the image, where the key is the attribute name
+		 *              and the value is the attribute value.
+		 */
+		return apply_filters( 'jetpack_lazy_images_new_attributes', $attributes );
+	}
+
+	/**
+	 * Adds JavaScript to check if the current browser supports JavaScript as well as some styles to hide lazy
+	 * images when the browser does not support JavaScript.
+	 *
+	 * @return void
+	 */
+	public function add_nojs_fallback() {
+		?>
+			<style type="text/css">
+				/* If html does not have either class, do not show lazy loaded images. */
+				html:not( .jetpack-lazy-images-js-enabled ):not( .js ) .jetpack-lazy-image {
+					display: none;
+				}
+			</style>
+			<script>
+				document.documentElement.classList.add(
+					'jetpack-lazy-images-js-enabled'
+				);
+			</script>
+		<?php
+	}
+
+	/**
+	 * Retrieves the placeholder image after running it through the lazyload_images_placeholder_image filter.
+	 *
+	 * @return string The placeholder image source.
+	 */
+	private static function get_placeholder_image() {
+		/**
+		 * Allows plugins and themes to modify the placeholder image.
+		 *
+		 * This filter is not prefixed with jetpack_ to provide a smoother migration
+		 * process from the WordPress Lazy Load plugin.
+		 *
+		 * @module lazy-images
+		 *
+		 * @since 5.6.0
+		 * @since 6.5.0 Default image is now a base64 encoded transparent gif.
+		 *
+		 * @param string The URL to the placeholder image
+		 */
+		return apply_filters(
+			'lazyload_images_placeholder_image',
+			'data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7'
+		);
+	}
+
+	private static function flatten_kses_hair_data( $attributes ) {
+		$flattened_attributes = array();
+		foreach ( $attributes as $name => $attribute ) {
+			$flattened_attributes[ $name ] = $attribute['value'];
+		}
+		return $flattened_attributes;
+	}
+
+	private static function build_attributes_string( $attributes ) {
+		$string = array();
+		foreach ( $attributes as $name => $value ) {
+			if ( '' === $value ) {
+				$string[] = sprintf( '%s', $name );
+			} else {
+				$string[] = sprintf( '%s="%s"', $name, esc_attr( $value ) );
+			}
+		}
+		return implode( ' ', $string );
+	}
+
+	public function enqueue_assets() {
+		wp_enqueue_script(
+			'jetpack-lazy-images',
+			Assets::get_file_url_for_environment(
+				'_inc/build/lazy-images/js/lazy-images.min.js',
+				'modules/lazy-images/js/lazy-images.js'
+			),
+			array( 'jquery' ),
+			JETPACK__VERSION,
+			true
+		);
+	}
+}