levendist.js

// Levenshtein Distance
// https://en.wikipedia.org/wiki/Levenshtein_distance
function distance(a, b) {
	if (!a.length || !b.length) {
		return 0;
	}

	const cost = a[a.length - 1] === b[b.length - 1] ? 0 : 1;
	const atrim = a.slice(0, a.length - 1);
	const btrim = b.slice(0, b.length - 1);
	return Math.min(
		distance(atrim, b) + 1,
		distance(a, btrim) + 1,
		distance(atrim, btrim) + cost
	);
}

distance("sitting", "kitten") === 3;