String Distance

gistfile1.js

    stringDistance: function(s1, s2) {
      // sift3: http://siderite.blogspot.com/2007/04/super-fast-and-accurate-string-distance.html
      if (s1 == null || s1.length === 0) {
        if (s2 == null || s2.length === 0) {
          return 0;
        } else {
          return s2.length;
        }
      }

      if (s2 == null || s2.length === 0) {
        return s1.length;
      }

      var c = 0;
      var offset1 = 0;
      var offset2 = 0;
      var lcs = 0;
      var maxOffset = 5;

      while ((c + offset1 < s1.length) && (c + offset2 < s2.length)) {
        if (s1[c + offset1] == s2[c + offset2]) {
          lcs++;
        } else {
          offset1 = 0;
          offset2 = 0;
          for (var i = 0; i < maxOffset; i++) {
            if ((c + i < s1.length) && (s1[c + i] == s2[c])) {
              offset1 = i;
              break;
            }
            if ((c + i < s2.length) && (s1[c] == s2[c + i])) {
              offset2 = i;
              break;
            }
          }
        }
        c++;
      }
      return (s1.length + s2.length) /2 - lcs;
    }