132 lines
3.5 KiB
JavaScript
132 lines
3.5 KiB
JavaScript
// modified to work without type="module"
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;(function () {
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/*! instant.page v1.2.2 - (C) 2019 Alexandre Dieulot - https://instant.page/license */
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var urlToPreload
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var mouseoverTimer
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var lastTouchTimestamp
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var prefetcher = document.createElement('link')
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var isSupported = prefetcher.relList && prefetcher.relList.supports && prefetcher.relList.supports('prefetch')
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var isDataSaverEnabled = navigator.connection && navigator.connection.saveData
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var allowQueryString = 'instantAllowQueryString' in document.body.dataset
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var allowExternalLinks = 'instantAllowExternalLinks' in document.body.dataset
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if (isSupported && !isDataSaverEnabled) {
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prefetcher.rel = 'prefetch'
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document.head.appendChild(prefetcher)
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var eventListenersOptions = {
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capture: true,
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passive: true
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}
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document.addEventListener('touchstart', touchstartListener, eventListenersOptions)
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document.addEventListener('mouseover', mouseoverListener, eventListenersOptions)
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}
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function touchstartListener (event) {
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/* Chrome on Android calls mouseover before touchcancel so `lastTouchTimestamp`
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* must be assigned on touchstart to be measured on mouseover. */
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lastTouchTimestamp = performance.now()
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var linkElement = event.target.closest('a')
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if (!isPreloadable(linkElement)) {
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return
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}
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linkElement.addEventListener('touchcancel', touchendAndTouchcancelListener, { passive: true })
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linkElement.addEventListener('touchend', touchendAndTouchcancelListener, { passive: true })
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urlToPreload = linkElement.href
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preload(linkElement.href)
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}
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function touchendAndTouchcancelListener () {
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urlToPreload = undefined
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stopPreloading()
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}
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function mouseoverListener (event) {
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if (performance.now() - lastTouchTimestamp < 1100) {
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return
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}
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var linkElement = event.target.closest('a')
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if (!isPreloadable(linkElement)) {
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return
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}
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linkElement.addEventListener('mouseout', mouseoutListener, { passive: true })
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urlToPreload = linkElement.href
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mouseoverTimer = setTimeout(function () {
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preload(linkElement.href)
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mouseoverTimer = undefined
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}, 65)
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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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} else {
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urlToPreload = undefined
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stopPreloading()
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}
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}
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function isPreloadable (linkElement) {
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if (!linkElement || !linkElement.href) {
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return
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}
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if (urlToPreload === linkElement.href) {
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return
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}
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var preloadLocation = new URL(linkElement.href)
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if (!allowExternalLinks && preloadLocation.origin !== location.origin && !('instant' in linkElement.dataset)) {
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return
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}
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if (!['http:', 'https:'].includes(preloadLocation.protocol)) {
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return
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}
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if (preloadLocation.protocol === 'http:' && location.protocol === 'https:') {
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return
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}
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if (!allowQueryString && preloadLocation.search && !('instant' in linkElement.dataset)) {
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return
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}
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if (preloadLocation.hash && preloadLocation.pathname + preloadLocation.search === location.pathname + location.search) {
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return
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}
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if ('noInstant' in linkElement.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) {
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prefetcher.href = url
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}
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function stopPreloading () {
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prefetcher.removeAttribute('href')
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}
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})()
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