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

levenshtein.js

// https://gist.github.com/andrei-m/982927#gistcomment-1931258 looks like the fastest Levenshtein implementation
const levenshtein = (a, b) => {
  if (a.length === 0) return b.length
  if (b.length === 0) return a.length
  let tmp, i, j, prev, val
  // swap to save some memory O(min(a,b)) instead of O(a)
  if (a.length > b.length) {
    tmp = a
    a = b
    b = tmp
  }

  row = Array(a.length + 1)
  // init the row
  for (i = 0; i <= a.length; i++) {
    row[i] = i
  }

  // fill in the rest
  for (i = 1; i <= b.length; i++) {
    prev = i
    for (j = 1; j <= a.length; j++) {
      if (b[i-1] === a[j-1]) {
        val = row[j-1] // match
      } else {
        val = Math.min(row[j-1] + 1, // substitution
              Math.min(prev + 1,     // insertion
                       row[j] + 1))  // deletion
      }
      row[j - 1] = prev
      prev = val
    }
    row[a.length] = prev
  }
  return row[a.length]
}