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/*! instant.page v5.1.1 - (C) 2019-2020 Alexandre Dieulot - https://instant.page/license */
let mouseoverTimer
let lastTouchTimestamp
const prefetches = new Set()
const prefetchElement = document.createElement('link')
const isSupported = prefetchElement.relList && prefetchElement.relList.supports && prefetchElement.relList.supports('prefetch')
&& window.IntersectionObserver && 'isIntersecting' in IntersectionObserverEntry.prototype
const allowQueryString = 'instantAllowQueryString' in document.body.dataset
const allowExternalLinks = 'instantAllowExternalLinks' in document.body.dataset
const useWhitelist = 'instantWhitelist' in document.body.dataset
const mousedownShortcut = 'instantMousedownShortcut' in document.body.dataset
const DELAY_TO_NOT_BE_CONSIDERED_A_TOUCH_INITIATED_ACTION = 1111
let delayOnHover = 65
let useMousedown = false
let useMousedownOnly = false
let useViewport = false
if ('instantIntensity' in document.body.dataset) {
const intensity = document.body.dataset.instantIntensity
if (intensity.substr(0, 'mousedown'.length) == 'mousedown') {
useMousedown = true
if (intensity == 'mousedown-only') {
useMousedownOnly = true
}
}
else if (intensity.substr(0, 'viewport'.length) == 'viewport') {
if (!(navigator.connection && (navigator.connection.saveData || (navigator.connection.effectiveType && navigator.connection.effectiveType.includes('2g'))))) {
if (intensity == "viewport") {
/* Biggest iPhone resolution (which we want): 414 × 896 = 370944
* Small 7" tablet resolution (which we don’t want): 600 × 1024 = 614400
* Note that the viewport (which we check here) is smaller than the resolution due to the UI’s chrome */
if (document.documentElement.clientWidth * document.documentElement.clientHeight < 450000) {
useViewport = true
}
}
else if (intensity == "viewport-all") {
useViewport = true
}
}
}
else {
const milliseconds = parseInt(intensity)
if (!isNaN(milliseconds)) {
delayOnHover = milliseconds
}
}
}
if (isSupported) {
const eventListenersOptions = {
capture: true,
passive: true,
}
if (!useMousedownOnly) {
document.addEventListener('touchstart', touchstartListener, eventListenersOptions)
}
if (!useMousedown) {
document.addEventListener('mouseover', mouseoverListener, eventListenersOptions)
}
else if (!mousedownShortcut) {
document.addEventListener('mousedown', mousedownListener, eventListenersOptions)
}
if (mousedownShortcut) {
document.addEventListener('mousedown', mousedownShortcutListener, eventListenersOptions)
}
if (useViewport) {
let triggeringFunction
if (window.requestIdleCallback) {
triggeringFunction = (callback) => {
requestIdleCallback(callback, {
timeout: 1500,
})
}
}
else {
triggeringFunction = (callback) => {
callback()
}
}
triggeringFunction(() => {
const intersectionObserver = new IntersectionObserver((entries) => {
entries.forEach((entry) => {
if (entry.isIntersecting) {
const linkElement = entry.target
intersectionObserver.unobserve(linkElement)
preload(linkElement.href)
}
})
})
document.querySelectorAll('a').forEach((linkElement) => {
if (isPreloadable(linkElement)) {
intersectionObserver.observe(linkElement)
}
})
})
}
}
function touchstartListener(event) {
/* Chrome on Android calls mouseover before touchcancel so `lastTouchTimestamp`
* must be assigned on touchstart to be measured on mouseover. */
lastTouchTimestamp = performance.now()
const linkElement = event.target.closest('a')
if (!isPreloadable(linkElement)) {
return
}
preload(linkElement.href)
}
function mouseoverListener(event) {
if (performance.now() - lastTouchTimestamp < DELAY_TO_NOT_BE_CONSIDERED_A_TOUCH_INITIATED_ACTION) {
return
}
if (!('closest' in event.target)) {
// Without this check sometimes an error “event.target.closest is not a function” is thrown, for unknown reasons
// That error denotes that `event.target` isn’t undefined. My best guess is that it’s the Document.
// Details could be gleaned from throwing such an error:
//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}`)
return
}
const linkElement = event.target.closest('a')
if (!isPreloadable(linkElement)) {
return
}
linkElement.addEventListener('mouseout', mouseoutListener, {passive: true})
mouseoverTimer = setTimeout(() => {
preload(linkElement.href)
mouseoverTimer = undefined
}, delayOnHover)
}
function mousedownListener(event) {
const linkElement = event.target.closest('a')
if (!isPreloadable(linkElement)) {
return
}
preload(linkElement.href)
}
function mouseoutListener(event) {
if (event.relatedTarget && event.target.closest('a') == event.relatedTarget.closest('a')) {
return
}
if (mouseoverTimer) {
clearTimeout(mouseoverTimer)
mouseoverTimer = undefined
}
}
function mousedownShortcutListener(event) {
if (performance.now() - lastTouchTimestamp < DELAY_TO_NOT_BE_CONSIDERED_A_TOUCH_INITIATED_ACTION) {
return
}
const linkElement = event.target.closest('a')
if (event.which > 1 || event.metaKey || event.ctrlKey) {
return
}
if (!linkElement) {
return
}
linkElement.addEventListener('click', function (event) {
if (event.detail == 1337) {
return
}
event.preventDefault()
}, {capture: true, passive: false, once: true})
const customEvent = new MouseEvent('click', {view: window, bubbles: true, cancelable: false, detail: 1337})
linkElement.dispatchEvent(customEvent)
}
function isPreloadable(linkElement) {
if (!linkElement || !linkElement.href) {
return
}
if (useWhitelist && !('instant' in linkElement.dataset)) {
return
}
if (!allowExternalLinks && linkElement.origin != location.origin && !('instant' in linkElement.dataset)) {
return
}
if (!['http:', 'https:'].includes(linkElement.protocol)) {
return
}
if (linkElement.protocol == 'http:' && location.protocol == 'https:') {
return
}
if (!allowQueryString && linkElement.search && !('instant' in linkElement.dataset)) {
return
}
if (linkElement.hash && linkElement.pathname + linkElement.search == location.pathname + location.search) {
return
}
if ('noInstant' in linkElement.dataset) {
return
}
return true
}
function preload(url) {
if (prefetches.has(url)) {
return
}
const prefetcher = document.createElement('link')
prefetcher.rel = 'prefetch'
prefetcher.href = url
document.head.appendChild(prefetcher)
prefetches.add(url)
}