62 lines
1.6 KiB
JavaScript
62 lines
1.6 KiB
JavaScript
/*
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* Top bar title auto change while scrolling up/down in mobile screens.
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*/
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$(function() {
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const titleSelector = "div.post>h1:first-of-type";
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const $pageTitle = $(titleSelector);
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const $topbarTitle = $("#topbar-title");
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if ($pageTitle.length === 0 /* on Home page */
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|| $pageTitle.hasClass("dynamic-title")
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|| $topbarTitle.is(":hidden")) {/* not in mobile views */
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return;
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}
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const defaultTitleText = $topbarTitle.text().trim();
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let titleText = $pageTitle.text().trim();
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let hasScrolled = false;
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let lastScrollTop = 0;
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if ($("#page-category").length || $("#page-tag").length) {
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/* The title in Category or Tag page will be "<title> <count_of_posts>" */
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if (/\s/.test(titleText)) {
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titleText = titleText.replace(/[0-9]/g, "").trim();
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}
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}
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let options = {
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rootMargin: '-48px 0px 0px 0px', // 48px equals to the topbar height (3rem)
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threshold: [0, 1]
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};
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let observer = new IntersectionObserver((entries) => {
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if (!hasScrolled) {
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hasScrolled = true;
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return;
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}
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let curScrollTop = $(window).scrollTop();
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let isScrollDown = lastScrollTop < curScrollTop;
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lastScrollTop = curScrollTop;
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let heading = entries[0];
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if (isScrollDown) {
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if (heading.intersectionRatio === 0) {
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$topbarTitle.text(titleText);
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}
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} else {
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if (heading.intersectionRatio === 1) {
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$topbarTitle.text(defaultTitleText);
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}
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}
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}, options);
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observer.observe(document.querySelector(titleSelector));
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/* Click title will scroll to top */
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$topbarTitle.click(function() {
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$("body,html").animate({scrollTop: 0}, 800);
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});
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});
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