Levenshtein distance between two given strings implemented in JavaScript and usable as a Node.js module

levenshtein.ts

/**
 * Computes the Levenshtein distance between two strings (a number that tells you how different two strings are).
 * The higher the number, the more different the two strings are.
 * Original source: https://gist.github.com/andrei-m/982927/0efdf215b00e5d34c90fdc354639f87ddc3bd0a5
 */
const getLevenshteinDistance = (a: string, b: string): number => {
  if (a.length == 0) return b.length;
  if (b.length == 0) return a.length;

  const matrix = [];

  // increment along the first column of each row
  let i;
  for (i = 0; i <= b.length; i++) {
    matrix[i] = [i];
  }

  // increment each column in the first row
  let j;
  for (j = 0; j <= a.length; j++) {
    matrix[0][j] = j;
  }

  // Fill in the rest of the matrix
  for (i = 1; i <= b.length; i++) {
    for (j = 1; j <= a.length; 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] + 1, // substitution
          Math.min(
            matrix[i][j - 1] + 1, // insertion
            matrix[i - 1][j] + 1
          )
        ); // deletion
      }
    }
  }

  return matrix[b.length][a.length];
};

export default getLevenshteinDistance;