62 lines
1.6 KiB
JavaScript
62 lines
1.6 KiB
JavaScript
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/* eslint-env browser */
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/**
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* Nav/Title replacement
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* Used on invividual post pages, displays the post title in place of the nav
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* bar when scrolling past the title
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*
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* Usage:
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* ```
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* Casper.stickyTitle({
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* navSelector: '.site-nav-main',
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* titleSelector: '.post-full-title',
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* activeClass: 'nav-post-title-active'
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* });
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* ```
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*/
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(function (window, document) {
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// set up Casper as a global object
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if (!window.Casper) {
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window.Casper = {};
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}
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window.Casper.stickyNavTitle = function stickyNavTitle(options) {
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var nav = document.querySelector(options.navSelector);
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var title = document.querySelector(options.titleSelector);
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var lastScrollY = window.scrollY;
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var ticking = false;
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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 requestTick() {
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if (!ticking) {
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requestAnimationFrame(update);
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}
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ticking = true;
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}
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function update() {
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var trigger = title.getBoundingClientRect().top + window.scrollY;
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var triggerOffset = title.offsetHeight + 35;
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// show/hide post title
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if (lastScrollY >= trigger + triggerOffset) {
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nav.classList.add(options.activeClass);
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} else {
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nav.classList.remove(options.activeClass);
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}
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ticking = false;
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}
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window.addEventListener('scroll', onScroll, {passive: true});
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update();
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};
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})(window, document);
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