vfrag/src/computeTargets.js

Paginate a document by breaking one or more containers vertically into multiple fragments.

import * as util from "./util.js";

export default function computeTargets (root = document.documentElement) {
	let info = {};
	let timer = util.timer();
	let links = root.querySelectorAll("a[href^='#']:not(.page > .page-number)");

	for (let a of links) {
		// Why not querySelector? So we don’t get errors for invalid selectors
		let target = document.getElementById(a.hash.slice(1));

		if (target) {
			let pageNumber = target.closest("[data-page]")?.dataset.page;

			if (pageNumber) {
				a.dataset.targetPage = pageNumber;

				if (a.matches('[data-page-target=""] *')) {
					// An empty data-page-target on a parent means we need to update that too
					// This is useful for TOCs where we want the page target on the <li>, not the <a>
					let parent = a.closest('[data-page-target=""]');
					parent.dataset.targetPage = pageNumber;
				}
			}
		}
	}

	info.links = links.length;
	console.info(`Computed target pages for ${ info.links } links in ${ timer.end() }`);
	return info;
}