levenshteinDistance.js

function d(s1, s2) {
  return function _d(m, n) {
    if (m == 0) {
      return n
    }
    if (n == 0) {
      return m
    }
    return Math.min(
      _d(m, n - 1) + 1,
      _d(m - 1, n) + 1,
      _d(m - 1, n - 1) + (s1[m - 1] === s2[n - 1] ? 0 : 1)
    )
  }(s1.length, s2.length)
}