ImageURLsFromHTML.js

/**
 * Return array of URLs found in HTML string
 *
 * If `<img>` wrapped into `<a>` uses `[href]` of `<a>` if it's an image
 *
 * @param {string} html
 * @returns {string[]}
 */
async ImageURLsFromHTML(html) {
	try {
		const allowedImageTypes = [
			'image/jpeg',
			'image/jpg',
			'image/png',
			'image/webp',
		]
		const urls = []
		await posthtml()
			.use(async tree => {
				tree.walk(node => {
					// TODO don't return img[src] if it's child of a[href] having image content-type
					if (node.tag === 'a') {
						const a = node
						const src = a.attrs.href
						// Node has <img> child
						if (node.content.find(node => (
							typeof node === 'object' &&
							node.tag === 'img' &&
							node.attrs.src
						))) {
							// TODO ensure it works
							(async function() {
								const request = await Promise.resolve(fetch(src, {
									method: 'HEAD',
								}))
								const headers = request.headers
								const contentType = headers.get('Content-Type')
								if (allowedImageTypes.includes(contentType)) {
									urls.push(src)
								}
							}())
						}
					} else if (
						node.tag === 'img' &&
						node.attrs.src
					) {
						urls.push(node.attrs.src)
					}
					return node
				})
				return tree
			})
			.process(html)
		return urls
	} catch (error) {
		console.error(error)
	}
}