336 lines
12 KiB
Plaintext
336 lines
12 KiB
Plaintext
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/* instant.page v5.2.0 - (C) 2019-2023 Alexandre Dieulot - https://instant.page/license */
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/* Custom modified version created for Super page Cache for Cloudflare plugin - Saumya Majumder */
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let _chromiumMajorVersionInUserAgent = null
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, _allowQueryString
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, _allowExternalLinks
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, _useWhitelist
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, _delayOnHover = 65
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, _lastTouchTimestamp
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, _mouseoverTimer
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, _preloadedList = new Set()
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const DELAY_TO_NOT_BE_CONSIDERED_A_TOUCH_INITIATED_ACTION = 1111
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init()
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function init() {
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const isSupported = document.createElement('link').relList.supports('prefetch')
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// instant.page is meant to be loaded with <script type=module>
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// (though sometimes webmasters load it as a regular script).
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// So it’s normally executed (and must not cause JavaScript errors) in:
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// - Chromium 61+
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// - Gecko in Firefox 60+
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// - WebKit in Safari 10.1+ (iOS 10.3+, macOS 10.10+)
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//
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// The check above used to check for IntersectionObserverEntry.isIntersecting
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// but module scripts support implies this compatibility — except in Safari
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// 10.1–12.0, but this prefetch check takes care of it.
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if (!isSupported) {
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return
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}
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const handleVaryAcceptHeader = 'instantVaryAccept' in document.body.dataset || 'Shopify' in window
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// The `Vary: Accept` header when received in Chromium 79–109 makes prefetches
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// unusable, as Chromium used to send a different `Accept` header.
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// It’s applied on all Shopify sites by default, as Shopify is very popular
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// and is the main source of this problem.
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// `window.Shopify` only exists on “classic” Shopify sites. Those using
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// Hydrogen (Remix SPA) aren’t concerned.
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const chromiumUserAgentIndex = navigator.userAgent.indexOf('Chrome/')
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if (chromiumUserAgentIndex > -1) {
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_chromiumMajorVersionInUserAgent = parseInt(navigator.userAgent.substring(chromiumUserAgentIndex + 'Chrome/'.length))
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}
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// The user agent client hints API is a theoretically more reliable way to
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// get Chromium’s version… but it’s not available in Samsung Internet 20.
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// It also requires a secure context, which would make debugging harder,
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// and is only available in recent Chromium versions.
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// In practice, Chromium browsers never shy from announcing "Chrome" in
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// their regular user agent string, as that maximizes their compatibility.
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if (handleVaryAcceptHeader && _chromiumMajorVersionInUserAgent && _chromiumMajorVersionInUserAgent < 110) {
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return
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}
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const mousedownShortcut = 'instantMousedownShortcut' in document.body.dataset
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_allowQueryString = 'instantAllowQueryString' in document.body.dataset
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_allowExternalLinks = 'instantAllowExternalLinks' in document.body.dataset
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_useWhitelist = 'instantWhitelist' in document.body.dataset
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const eventListenersOptions = {
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capture: true,
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passive: true,
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}
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let useMousedown = false
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let useMousedownOnly = false
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let useViewport = false
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if ('instantIntensity' in document.body.dataset) {
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const intensity = document.body.dataset.instantIntensity
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if (intensity.startsWith('mousedown')) {
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useMousedown = true
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if (intensity == 'mousedown-only') {
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useMousedownOnly = true
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}
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}
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else if (intensity.startsWith('viewport')) {
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const isNavigatorConnectionSaveDataEnabled = navigator.connection && navigator.connection.saveData
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const isNavigatorConnectionLike2g = navigator.connection && navigator.connection.effectiveType && navigator.connection.effectiveType.includes('2g')
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if (!isNavigatorConnectionSaveDataEnabled && !isNavigatorConnectionLike2g) {
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if (intensity == "viewport") {
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if (document.documentElement.clientWidth * document.documentElement.clientHeight < 450000) {
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useViewport = true
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// Smartphones are the most likely to have a slow connection, and
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// their small screen size limits the number of links (and thus
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// server load).
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//
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// Foldable phones (being expensive as of 2023), tablets and PCs
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// generally have a decent connection, and a big screen displaying
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// more links that would put more load on the server.
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//
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// iPhone 14 Pro Max (want): 430×932 = 400 760
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// Samsung Galaxy S22 Ultra with display size set to 80% (want):
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// 450×965 = 434 250
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// Small tablet (don’t want): 600×960 = 576 000
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// Those number are virtual screen size, the viewport (used for
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// the check above) will be smaller with the browser’s interface.
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}
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}
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else if (intensity == "viewport-all") {
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useViewport = true
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}
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}
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}
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else {
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const milliseconds = parseInt(intensity)
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if (!isNaN(milliseconds)) {
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_delayOnHover = milliseconds
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}
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}
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}
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if (!useMousedownOnly) {
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document.addEventListener('touchstart', touchstartListener, eventListenersOptions)
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}
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if (!useMousedown) {
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document.addEventListener('mouseover', mouseoverListener, eventListenersOptions)
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}
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else if (!mousedownShortcut) {
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document.addEventListener('mousedown', mousedownListener, eventListenersOptions)
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}
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if (mousedownShortcut) {
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document.addEventListener('mousedown', mousedownShortcutListener, eventListenersOptions)
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}
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if (useViewport) {
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let requestIdleCallbackOrFallback = window.requestIdleCallback
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// Safari has no support as of 16.3: https://webkit.org/b/164193
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if (!requestIdleCallbackOrFallback) {
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requestIdleCallbackOrFallback = (callback) => {
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callback()
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// A smarter fallback like setTimeout is not used because devices that
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// may eventually be eligible to a Safari version supporting prefetch
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// will be very powerful.
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// The weakest devices that could be eligible are the 2017 iPad and
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// the 2016 MacBook.
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}
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}
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requestIdleCallbackOrFallback(function observeIntersection() {
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const intersectionObserver = new IntersectionObserver((entries) => {
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entries.forEach((entry) => {
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if (entry.isIntersecting) {
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const anchorElement = entry.target
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intersectionObserver.unobserve(anchorElement)
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preload(anchorElement.href)
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}
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})
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})
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document.querySelectorAll('a').forEach((anchorElement) => {
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if (isPreloadable(anchorElement)) {
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intersectionObserver.observe(anchorElement)
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}
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})
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}, {
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timeout: 1500,
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})
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}
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}
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function touchstartListener(event) {
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_lastTouchTimestamp = performance.now()
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// Chrome on Android triggers mouseover before touchcancel, so
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// `_lastTouchTimestamp` must be assigned on touchstart to be measured
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// on mouseover.
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const anchorElement = event.target.closest('a')
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if (!isPreloadable(anchorElement)) {
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return
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}
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preload(anchorElement.href, 'high')
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}
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function mouseoverListener(event) {
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if (performance.now() - _lastTouchTimestamp < DELAY_TO_NOT_BE_CONSIDERED_A_TOUCH_INITIATED_ACTION) {
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return
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}
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if (!('closest' in event.target)) {
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return
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// Without this check sometimes an error “event.target.closest is not a function” is thrown, for unknown reasons
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// That error denotes that `event.target` isn’t undefined. My best guess is that it’s the Document.
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//
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// Details could be gleaned from throwing such an error:
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//throw new TypeError(`instant.page non-element event target: timeStamp=${~~event.timeStamp}, type=${event.type}, typeof=${typeof event.target}, nodeType=${event.target.nodeType}, nodeName=${event.target.nodeName}, viewport=${innerWidth}x${innerHeight}, coords=${event.clientX}x${event.clientY}, scroll=${scrollX}x${scrollY}`)
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}
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const anchorElement = event.target.closest('a')
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if (!isPreloadable(anchorElement)) {
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return
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}
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anchorElement.addEventListener('mouseout', mouseoutListener, {passive: true})
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_mouseoverTimer = setTimeout(() => {
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preload(anchorElement.href, 'high')
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_mouseoverTimer = undefined
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}, _delayOnHover)
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}
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function mousedownListener(event) {
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const anchorElement = event.target.closest('a')
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if (!isPreloadable(anchorElement)) {
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return
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}
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preload(anchorElement.href, 'high')
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}
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function mouseoutListener(event) {
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if (event.relatedTarget && event.target.closest('a') == event.relatedTarget.closest('a')) {
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return
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}
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if (_mouseoverTimer) {
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clearTimeout(_mouseoverTimer)
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_mouseoverTimer = undefined
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}
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}
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function mousedownShortcutListener(event) {
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if (performance.now() - _lastTouchTimestamp < DELAY_TO_NOT_BE_CONSIDERED_A_TOUCH_INITIATED_ACTION) {
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return
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}
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const anchorElement = event.target.closest('a')
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if (event.which > 1 || event.metaKey || event.ctrlKey) {
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return
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}
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if (!anchorElement) {
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return
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}
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anchorElement.addEventListener('click', function (event) {
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if (event.detail == 1337) {
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return
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}
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event.preventDefault()
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}, {capture: true, passive: false, once: true})
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const customEvent = new MouseEvent('click', {view: window, bubbles: true, cancelable: false, detail: 1337})
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anchorElement.dispatchEvent(customEvent)
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}
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function isPreloadable(anchorElement) {
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if (!anchorElement || !anchorElement.href) {
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return
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}
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if (_useWhitelist && !('instant' in anchorElement.dataset)) {
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return
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}
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if (anchorElement.origin != location.origin) {
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let allowed = _allowExternalLinks || 'instant' in anchorElement.dataset
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if (!allowed || !_chromiumMajorVersionInUserAgent) {
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// Chromium-only: see comment on “restrictive prefetch”
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return
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}
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}
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if (!['http:', 'https:'].includes(anchorElement.protocol)) {
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return
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}
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if (anchorElement.protocol == 'http:' && location.protocol == 'https:') {
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return
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}
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if (!_allowQueryString && anchorElement.search && !('instant' in anchorElement.dataset)) {
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return
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}
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if (anchorElement.hash && anchorElement.pathname + anchorElement.search == location.pathname + location.search) {
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return
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}
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if ('noInstant' in anchorElement.dataset) {
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return
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}
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return true
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}
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function preload(url, fetchPriority = 'auto') {
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if (_preloadedList.has(url)) {
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return
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}
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// Custom check added by Super Page Cache for Cloudflare plugin
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if( typeof swcfpc_can_url_be_prefetched === 'function' && swcfpc_can_url_be_prefetched(url.split("#")[0]) === false ) {
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return
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}
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const linkElement = document.createElement('link')
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linkElement.rel = 'prefetch'
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linkElement.href = url
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linkElement.fetchPriority = fetchPriority
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// By default, a prefetch is loaded with a low priority.
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// When there’s a fair chance that this prefetch is going to be used in the
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// near term (= after a touch/mouse event), giving it a high priority helps
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// make the page load faster in case there are other resources loading.
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// Prioritizing it implicitly means deprioritizing every other resource
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// that’s loading on the page. Due to HTML documents usually being much
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// smaller than other resources (notably images and JavaScript), and
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// prefetches happening once the initial page is sufficiently loaded,
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// this theft of bandwidth should rarely be detrimental.
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linkElement.as = 'document'
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// as=document is Chromium-only and allows cross-origin prefetches to be
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// usable for navigation. They call it “restrictive prefetch” and intend
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// to remove it: https://crbug.com/1352371
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//
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// This document from the Chrome team dated 2022-08-10
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// https://docs.google.com/document/d/1x232KJUIwIf-k08vpNfV85sVCRHkAxldfuIA5KOqi6M
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// claims (I haven’t tested) that data- and battery-saver modes as well as
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// the setting to disable preloading do not disable restrictive prefetch,
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// unlike regular prefetch. That’s good for prefetching on a touch/mouse
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// event, but might be bad when prefetching every link in the viewport.
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document.head.appendChild(linkElement)
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_preloadedList.add(url)
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}
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