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/*! instant.page v1.2.2 - (C) 2019 Alexandre Dieulot - https://instant.page/license */
let urlToPreload;
let mouseoverTimer;
let lastTouchTimestamp;
const prefetcher = document.createElement('link');
const isSupported = prefetcher.relList && prefetcher.relList.supports && prefetcher.relList.supports('prefetch');
const isDataSaverEnabled = navigator.connection && navigator.connection.saveData;
const allowQueryString = 'instantAllowQueryString' in document.body.dataset;
const allowExternalLinks = 'instantAllowExternalLinks' in document.body.dataset;
if (isSupported && !isDataSaverEnabled) {
prefetcher.rel = 'prefetch';
document.head.appendChild(prefetcher);
const eventListenersOptions = {
capture: true,
passive: true,
};
document.addEventListener('touchstart', touchstartListener, eventListenersOptions);
document.addEventListener('mouseover', mouseoverListener, eventListenersOptions)
}
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
}
linkElement.addEventListener('touchcancel', touchendAndTouchcancelListener, {passive: true});
linkElement.addEventListener('touchend', touchendAndTouchcancelListener, {passive: true});
urlToPreload = linkElement.href;
preload(linkElement.href)
}
function touchendAndTouchcancelListener() {
urlToPreload = undefined;
stopPreloading()
}
function mouseoverListener(event) {
if (performance.now() - lastTouchTimestamp < 1100) {
return
}
const linkElement = event.target.closest('a');
if (!isPreloadable(linkElement)) {
return
}
linkElement.addEventListener('mouseout', mouseoutListener, {passive: true});
urlToPreload = linkElement.href;
mouseoverTimer = setTimeout(() => {
preload(linkElement.href);
mouseoverTimer = undefined
}, 65)
}
function mouseoutListener(event) {
if (event.relatedTarget && event.target.closest('a') === event.relatedTarget.closest('a')) {
return
}
if (mouseoverTimer) {
clearTimeout(mouseoverTimer);
mouseoverTimer = undefined
} else {
urlToPreload = undefined;
stopPreloading()
}
}
function isPreloadable(linkElement) {
if (!linkElement || !linkElement.href) {
return
}
if (urlToPreload === linkElement.href) {
return
}
const preloadLocation = new URL(linkElement.href);
if (!allowExternalLinks && preloadLocation.origin !== location.origin && !('instant' in linkElement.dataset)) {
return
}
if (!['http:', 'https:'].includes(preloadLocation.protocol)) {
return
}
if (preloadLocation.protocol === 'http:' && location.protocol === 'https:') {
return
}
if (!allowQueryString && preloadLocation.search && !('instant' in linkElement.dataset)) {
return
}
if (preloadLocation.hash && preloadLocation.pathname + preloadLocation.search === location.pathname + location.search) {
return
}
if ('noInstant' in linkElement.dataset) {
return
}
return true
}
function preload(url) {
prefetcher.href = url
}
function stopPreloading() {
prefetcher.removeAttribute('href')
}
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