DOM TreeWalker API from Oak

toc.js.oak

{
	loop: loop
} := import('std')

// headingsList takes some container <div> and returns a list of all headings
// within that section of the page, in order
fn headingsList(div) {
	walker := document.createTreeWalker(
		div
		NodeFilter.SHOW_ELEMENT
		{
			acceptNode: fn(el) if el.tagName {
				'H1', 'H2', 'H3', 'H4', 'H5', 'H6' -> NodeFilter.FILTER_ACCEPT
				_ -> NodeFilter.FILTER_SKIP
			}
		}
	)

	headings := []
	with loop() fn(_, break) if el := walker.nextNode() {
		? -> break(headings)
		_ -> headings << {
			level: int(el.tagName.1)
			text: el.textContent
		}
	}
}