Levenshtein distance implemented in TypeScript

levenshtein.ts

export function levenshtein(a: string, b: string): number
{
	const an = a ? a.length : 0;
	const bn = b ? b.length : 0;
	if (an === 0)
	{
		return bn;
	}
	if (bn === 0)
	{
		return an;
	}
	const matrix = new Array<number[]>(bn + 1);
	for (let i = 0; i <= bn; ++i)
	{
		let row = matrix[i] = new Array<number>(an + 1);
		row[0] = i;
	}
	const firstRow = matrix[0];
	for (let j = 1; j <= an; ++j)
	{
		firstRow[j] = j;
	}
	for (let i = 1; i <= bn; ++i)
	{
		for (let j = 1; j <= an; ++j)
		{
			if (b.charAt(i - 1) === a.charAt(j - 1))
			{
				matrix[i][j] = matrix[i - 1][j - 1];
			}
			else
			{
				matrix[i][j] = Math.min(
					matrix[i - 1][j - 1], // substitution
					matrix[i][j - 1], // insertion
					matrix[i - 1][j] // deletion
				) + 1;
			}
		}
	}
	return matrix[bn][an];
};

Very simple and practical implementation of the Levenshtein algorithm ! Thanks

Would you mind if I used this in an NPM package that I'm developing? Credit will be given above the function of course.

Would you mind if I used this in an NPM package that I'm developing? Credit will be given above the function of course.

I am certain I just translated this from someone else's implementation in another language. Wish I could remember.

You can have it, no need to credit me.

Cleaned up a little, and honored noUncheckedIndexedAccess

export function levenshtein(a: string, b: string) {
	const an = a.length
	const bn = b.length
	if (an == 0) {
		return bn
	}
	if (bn == 0) {
		return an
	}
	const matrix = new Array<number[]>(bn + 1)
	for (let i = 0; i <= bn; ++i) {
		const row = (matrix[i] = new Array<number>(an + 1))
		row[0] = i
	}
	const firstRow = matrix[0]
	for (let j = 1; j <= an; ++j) {
		firstRow![j] = j
	}
	for (let i = 1; i <= bn; ++i) {
		for (let j = 1; j <= an; ++j) {
			if (b.charAt(i - 1) === a.charAt(j - 1)) {
				matrix[i]![j] = matrix[i - 1]![j - 1]!
			} else {
				matrix[i]![j] =
					Math.min(
						matrix[i - 1]![j - 1]!, // substitution
						matrix[i]![j - 1]!, // insertion
						matrix[i - 1]![j]! // deletion
					) + 1
			}
		}
	}
	return matrix[bn]![an]!
}