Calculate Levenshtein Distance using iterative method

levenshtein_distance.js

function levenshteinDistance(a, b) {
  if (a.length === 0) return b.length; 
  if (b.length === 0) return a.length; 

  let matrix = [];
  
  for (let i = 0; i <= b.length; ++i) {
    matrix[i] = [i];
  }
  for (let j = 0; j <= a.length; ++j) {
    matrix[0][j] = j;
  }

  for (let i = 1; i <= b.length; ++i) {
    for (let j = 1; j <= a.length; ++j) {
      if (b[i-1] === a[j-1]) {
        matrix[i][j] = matrix[i-1][j-1];
      } else {
        matrix[i][j] = Math.min(
          matrix[i-1][j-1] + 1,
          matrix[i][j-1] + 1,
          matrix[i-1][j] + 1
        );
      }
    }
  }

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