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/* eslint-env browser */
import {filterMultipleArrays, stitchArrays} from '../../shared-util/sugar.js';
import {dispatchInternalEvent} from '../client-util.js';
export const info = {
id: 'hashLinkInfo',
links: null,
hrefs: null,
targets: null,
state: {
highlightedTarget: null,
scrollingAfterClick: false,
concludeScrollingStateInterval: null,
},
event: {
beforeHashLinkScrolls: [],
whenHashLinkClicked: [],
},
};
export function getPageReferences() {
info.links =
Array.from(document.querySelectorAll('a[href^="#"]:not([href="#"])'));
info.hrefs =
info.links
.map(link => link.getAttribute('href'));
info.targets =
info.hrefs
.map(href => document.getElementById(href.slice(1)));
filterMultipleArrays(
info.links,
info.hrefs,
info.targets,
(_link, _href, target) => target);
}
function processScrollingAfterHashLinkClicked() {
const {state} = info;
if (state.concludeScrollingStateInterval) return;
let lastScroll = window.scrollY;
state.scrollingAfterClick = true;
state.concludeScrollingStateInterval = setInterval(() => {
if (Math.abs(window.scrollY - lastScroll) < 10) {
clearInterval(state.concludeScrollingStateInterval);
state.scrollingAfterClick = false;
state.concludeScrollingStateInterval = null;
} else {
lastScroll = window.scrollY;
}
}, 200);
}
export function addPageListeners() {
// Instead of defining a scroll offset (to account for the sticky heading)
// in JavaScript, we interface with the CSS property 'scroll-margin-top'.
// This lets the scroll offset be consolidated where it makes sense, and
// sets an appropriate offset when (re)loading a page with hash for free!
const {state, event} = info;
for (const {hashLink, href, target} of stitchArrays({
hashLink: info.links,
href: info.hrefs,
target: info.targets,
})) {
hashLink.addEventListener('click', evt => {
if (evt.metaKey || evt.shiftKey || evt.ctrlKey || evt.altKey) {
return;
}
// Don't do anything if the target element isn't actually visible!
if (target.offsetParent === null) {
return;
}
// Allow event handlers to prevent scrolling.
const listenerResults =
dispatchInternalEvent(event, 'beforeHashLinkScrolls', {
link: hashLink,
target,
});
if (listenerResults.includes(false)) {
return;
}
// Hide skipper box right away, so the layout is updated on time for the
// math operations coming up next.
const skipper = document.getElementById('skippers');
skipper.style.display = 'none';
setTimeout(() => skipper.style.display = '');
const box = target.getBoundingClientRect();
const style = window.getComputedStyle(target);
const scrollY =
window.scrollY
+ box.top
- style['scroll-margin-top'].replace('px', '');
evt.preventDefault();
history.pushState({}, '', href);
window.scrollTo({top: scrollY, behavior: 'smooth'});
target.focus({preventScroll: true});
const maxScroll =
document.body.scrollHeight
- window.innerHeight;
if (scrollY > maxScroll && target.classList.contains('content-heading')) {
if (state.highlightedTarget) {
state.highlightedTarget.classList.remove('highlight-hash-link');
}
target.classList.add('highlight-hash-link');
state.highlightedTarget = target;
}
processScrollingAfterHashLinkClicked();
dispatchInternalEvent(event, 'whenHashLinkClicked', {
link: hashLink,
target,
});
});
}
for (const target of info.targets) {
target.addEventListener('animationend', evt => {
if (evt.animationName !== 'highlight-hash-link') return;
target.classList.remove('highlight-hash-link');
if (target !== state.highlightedTarget) return;
state.highlightedTarget = null;
});
}
}
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