Iterative Levenshtein Distance algorithm adapted from http://en.wikipedia.org/wiki/Levenshtein_distance

lev.js

// Iterative with two matrix rows
function lev(left, right) {
  
  // Degenerative Cases
  if (left == right) return 0;
  if (left.length == 0) return right.length;
  if (right.length == 0) return left.length;
  
  var vectorLength = right.length + 1;
  var workVector0 = new Array();
  var workVector1 = new Array();
  
  for (var i = 0; i < vectorLength; i++) {
    workVector0[i] = i;
  }
  
  for (var i = 0; i < left.length; i++) {
    
    workVector1[0] = i + 1;
    for (var j = 0; j < right.length; j++) {
      var cost = (left[i] == right[j]) ? 0 : 1;
      workVector1[j + 1] = Math.min(workVector1[j] + 1, workVector0[j + 1] + 1, workVector0[j] + cost);
    }
    
    for (var j = 0; j < vectorLength; j++) {
      workVector0[j] = workVector1[j];
    }
  }
  
  return workVector1[right.length];
}