30-seconds-of-code/snippets_archive/levenshteinDistance.md

levenshteinDistance

Calculates the Levenshtein distance between two strings.

Calculates the number of changes (substitutions, deletions or additions) required to convert string1 to string2. Can also be used to compare two strings as shown in the second example.

const levenshteinDistance = (string1, string2) => {
  if (string1.length === 0) return string2.length;
  if (string2.length === 0) return string1.length;
  let matrix = Array(string2.length + 1)
    .fill(0)
    .map((x, i) => [i]);
  matrix[0] = Array(string1.length + 1)
    .fill(0)
    .map((x, i) => i);
  for (let i = 1; i <= string2.length; i++) {
    for (let j = 1; j <= string1.length; j++) {
      if (string2[i - 1] === string1[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[string2.length][string1.length];
};

levenshteinDistance('30-seconds-of-code','30-seconds-of-python-code'); // 7
const compareStrings = (string1,string2) => (100 - levenshteinDistance(string1,string2) / Math.max(string1.length,string2.length));
compareStrings('30-seconds-of-code', '30-seconds-of-python-code'); // 99.72 (%)