97 lines
3.0 KiB
JavaScript
97 lines
3.0 KiB
JavaScript
/**
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* AKSRT Instant Page
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*
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* Lightweight page prefetch on hover/focus.
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* Preloads pages when the user hovers over a link, so navigation feels instant.
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* No external dependencies — pure vanilla JS.
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*
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* Based on the instant.page concept (MIT license).
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*
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* @package AKSRT
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*/
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(function () {
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'use strict';
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// Only prefetch on desktop (no touch-only devices) with good connection
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if ('connection' in navigator) {
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var conn = navigator.connection;
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if (conn.saveData || (conn.effectiveType && conn.effectiveType.indexOf('2g') !== -1)) return;
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}
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// Don't run on touch-only devices (they don't benefit from hover prefetch)
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var hasHoverSupport = window.matchMedia('(hover: hover) and (pointer: fine)').matches;
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if (!hasHoverSupport) return;
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var prefetcher = document.createElement('link');
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var isPrefetched = {};
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var timer = null;
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var DELAY = 65; // ms to wait before prefetching
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var MAX_PREFETCH = 3; // max concurrent prefetches
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var prefetchedCount = 0;
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if (!prefetcher.relList || !prefetcher.relList.supports || !prefetcher.relList.supports('prefetch')) return;
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function prefetch(url) {
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if (isPrefetched[url] || prefetchedCount >= MAX_PREFETCH) return;
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// Don't prefetch URLs with hash (same page navigation)
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if (url.indexOf('#') !== -1) return;
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// Only prefetch same-origin URLs
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try {
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var link = new URL(url, window.location.origin);
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if (link.origin !== window.location.origin) return;
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// Don't prefetch the current page
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if (link.pathname === window.location.pathname && link.search === window.location.search) return;
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} catch (e) { return; }
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// Don't prefetch files/downloads
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if (/\.(pdf|zip|rar|7z|tar|gz|exe|dmg|apk|mp[34]|avi|mov|wmv|flv|webm|ogg|wav|bmp|gif|ico|svg|woff2?|ttf|eot)(\?|$)/i.test(url)) return;
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isPrefetched[url] = true;
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prefetchedCount++;
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var linkEl = document.createElement('link');
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linkEl.rel = 'prefetch';
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linkEl.href = url;
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linkEl.as = 'document';
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document.head.appendChild(linkEl);
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}
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function onHoverStart(e) {
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var link = e.target.closest('a');
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if (!link || !link.href) return;
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if (link.target === '_blank') return;
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if (link.hasAttribute('download')) return;
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if (link.getAttribute('rel') === 'nofollow') return;
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if (link.closest('.no-prefetch,[data-no-prefetch]')) return;
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clearTimeout(timer);
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timer = setTimeout(function () {
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prefetch(link.href);
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}, DELAY);
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}
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function onHoverEnd() {
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clearTimeout(timer);
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}
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document.addEventListener('mouseover', onHoverStart, { passive: true, capture: true });
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document.addEventListener('mouseout', onHoverEnd, { passive: true, capture: true });
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// Also prefetch on focus for keyboard navigation
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document.addEventListener('focusin', function (e) {
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var link = e.target.closest('a');
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if (link && link.href) {
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prefetch(link.href);
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}
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}, { passive: true, capture: true });
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// Cleanup after page hides (bfcache)
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window.addEventListener('pagehide', function () {
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isPrefetched = {};
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prefetchedCount = 0;
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});
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})();
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