110 lines
3.0 KiB
JavaScript
110 lines
3.0 KiB
JavaScript
/* eslint-env browser */
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/**
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* Infinite Scroll
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* Used on all pages where there is a list of posts (homepage, tag index, etc).
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*
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* When the page is scrolled to 300px from the bottom, the next page of posts
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* is fetched by following the the <link rel="next" href="..."> that is output
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* by {{ghost_head}}.
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*
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* The individual post items are extracted from the fetched pages by looking for
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* a wrapper element with the class "post-card". Any found elements are appended
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* to the element with the class "post-feed" in the currently viewed page.
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*/
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(function (window, document) {
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// next link element
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var nextElement = document.querySelector('link[rel=next]');
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if (!nextElement) {
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return;
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}
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// post feed element
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var feedElement = document.querySelector('.post-feed');
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if (!feedElement) {
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return;
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}
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var buffer = 300;
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var ticking = false;
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var loading = false;
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var lastScrollY = window.scrollY;
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var lastWindowHeight = window.innerHeight;
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var lastDocumentHeight = document.documentElement.scrollHeight;
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function onPageLoad() {
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if (this.status === 404) {
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window.removeEventListener('scroll', onScroll);
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window.removeEventListener('resize', onResize);
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return;
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}
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// append contents
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var postElements = this.response.querySelectorAll('.post-card');
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postElements.forEach(function (item) {
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feedElement.appendChild(item);
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});
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// set next link
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var resNextElement = this.response.querySelector('link[rel=next]');
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if (resNextElement) {
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nextElement.href = resNextElement.href;
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} else {
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window.removeEventListener('scroll', onScroll);
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window.removeEventListener('resize', onResize);
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}
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// sync status
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lastDocumentHeight = document.documentElement.scrollHeight;
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ticking = false;
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loading = false;
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}
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function onUpdate() {
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// return if already loading
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if (loading) {
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return;
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}
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// return if not scroll to the bottom
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if (lastScrollY + lastWindowHeight <= lastDocumentHeight - buffer) {
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ticking = false;
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return;
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}
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loading = true;
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var xhr = new window.XMLHttpRequest();
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xhr.responseType = 'document';
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xhr.addEventListener('load', onPageLoad);
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xhr.open('GET', nextElement.href);
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xhr.send(null);
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}
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function requestTick() {
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ticking || window.requestAnimationFrame(onUpdate);
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ticking = true;
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}
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function onScroll() {
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lastScrollY = window.scrollY;
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requestTick();
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}
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function onResize() {
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lastWindowHeight = window.innerHeight;
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lastDocumentHeight = document.documentElement.scrollHeight;
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requestTick();
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}
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window.addEventListener('scroll', onScroll, {passive: true});
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window.addEventListener('resize', onResize);
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requestTick();
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})(window, document);
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