Nodejs Utililty Methods String Levenshtein Distance

String.prototype.levenshtein = function()
  var s = this;
  var t = String(arguments[0] || '');
  var cuthalf = Number(arguments.callee.maxComparedLength) || t.length;
  s = s.substr(0, cuthalf);
  t = t.substr(0, cuthalf);
  var m = s.length;
  var n = t.length;
...

String.prototype.levenshtein = function(str){
    if (! str ){
      return false;
    str = str.toLowerCase().replace(/[^a-z]/g, "");
      var t = this.toLowerCase().replace(/[^a-z]/g, "");
      var i;
        var j;
        var cost;
...

String.prototype.levenshteinDistance = String.prototype.levenshteinDistance || function(c) {
  var s,
    l = (s = this.split("")).length,
    t = (c = c.split("")).length,
    i,
    j,
    m,
    n;
  if(!(l || t)) {
...