eleventy-plugin-backlinks/lib/get-backlinks.js

Collect and display backlinks from your notes

function caselessCompare(a, b) {
	return a.normalize().toLowerCase() === b.normalize().toLowerCase();
}

// This regex finds all wikilinks in a string
const wikilinkRegExp = /\[\[\s*([^\[\]\|\n\r]+)(\|[^\[\]\|\n\r]+)?\s*\]\]/g;

module.exports = function (options) {
	return async ({ collections, page }) => {
		const { notes } = collections;

		const fileStem = page.filePathStem.replace(`/${options.folder}/`, '');

		let backlinks = [];

		// Search the other notes for backlinks
		for (const otherNote of notes) {
			const noteContent = (await otherNote.template.read()).content;

			// Get all links from otherNote
			const outboundLinks = (noteContent.match(wikilinkRegExp) || []).map(
				(link) =>
					// Extract link location
					link
						.slice(2, -2)
						.split('|')[0]
						.replace(/\.(md|mkd|markdown|html|htm)\s*$/i, '')
						.replace(`/${options.folder}/`, '')
						.trim(),
			);

			// If the other note links here, return related info
			if (outboundLinks.some((link) => caselessCompare(link, fileStem))) {
				backlinks.push(options.getData(otherNote));
			}
		}

		return backlinks;
	};
};