60 lines
2 KiB
JavaScript
60 lines
2 KiB
JavaScript
import StickyFill from 'stickyfilljs';
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export const createPlaceholder = () => {
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const placeholder = document.createElement('div');
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placeholder.classList.add('sticky-placeholder');
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return placeholder;
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};
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export const isSticky = (el, scrollY, stickyTop, insertPlaceholder) => {
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const top = Math.floor(el.offsetTop - scrollY);
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if (top <= stickyTop && !el.classList.contains('is-stuck')) {
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const placeholder = insertPlaceholder ? createPlaceholder() : null;
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const heightBefore = el.offsetHeight;
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el.classList.add('is-stuck');
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if (insertPlaceholder) {
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el.parentNode.insertBefore(placeholder, el.nextElementSibling);
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placeholder.style.height = `${heightBefore - el.offsetHeight}px`;
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}
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} else if (top > stickyTop && el.classList.contains('is-stuck')) {
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el.classList.remove('is-stuck');
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if (insertPlaceholder && el.nextElementSibling && el.nextElementSibling.classList.contains('sticky-placeholder')) {
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el.nextElementSibling.remove();
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}
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}
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};
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/**
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* Create a listener that will toggle a 'is-stuck' class, based on the current scroll position.
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*
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* - If the current environment does not support `position: sticky`, do nothing.
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*
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* @param {HTMLElement} el The `position: sticky` element.
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* @param {Number} stickyTop Used to determine when an element is stuck.
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* @param {Boolean} insertPlaceholder Should a placeholder element be created when element is stuck?
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*/
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export const stickyMonitor = (el, stickyTop, insertPlaceholder = true) => {
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if (!el) return;
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if (typeof CSS === 'undefined' || !(CSS.supports('(position: -webkit-sticky) or (position: sticky)'))) return;
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document.addEventListener('scroll', () => isSticky(el, window.scrollY, stickyTop, insertPlaceholder), {
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passive: true,
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});
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};
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/**
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* Polyfill the `position: sticky` behavior.
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*
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* - If the current environment supports `position: sticky`, do nothing.
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* - Can receive an iterable element list (NodeList, jQuery collection, etc.) or single HTMLElement.
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*/
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export const polyfillSticky = (el) => {
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StickyFill.add(el);
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};
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