editdist.js

(function() {
  // Compute the levenshtein-damerau distance between the two given strings
  function getEditDistance(a, b) {
   /*
    * Found at: https://gist.github.com/andrei-m/982927
    *
    * Copyright (c) 2011 Andrei Mackenzie
    *
    * Permission is hereby granted, free of charge, to any person obtaining a
    * copy of this software and associated documentation files (the "Software"),
    * to deal in the Software without restriction, including without limitation
    * the rights to use, copy, modify, merge, publish, distribute, sublicense,
    * and/or sell copies of the Software, and to permit persons to whom the
    * Software is furnished to do so, subject to the following conditions:
    *
    * The above copyright notice and this permission notice shall be included in
    * all copies or substantial portions of the Software.
    *
    * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
    * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    * DEALINGS IN THE SOFTWARE.
    */
    if(a.length == 0) return b.length; 
    if(b.length == 0) return a.length; 
   
    var matrix = [];
   
    // increment along the first column of each row
    var i;
    for(i = 0; i <= b.length; i++){
      matrix[i] = [i];
    }
   
    // increment each column in the first row
    var j;
    for(j = 0; j <= a.length; j++){
      matrix[0][j] = j;
    }
   
    // Fill in the rest of the matrix
    for(i = 1; i <= b.length; i++){
      for(j = 1; j <= a.length; j++){
        if(b.charAt(i-1) == a.charAt(j-1)){
          matrix[i][j] = matrix[i-1][j-1];
        } else {
          matrix[i][j] = Math.min(matrix[i-1][j-1] + 1, // substitution
                                  Math.min(matrix[i][j-1] + 1, // insertion
                                           matrix[i-1][j] + 1)); // deletion
        }
        if (i > 1 && j > 1 && b.charAt(i-1) == a.charAt(j-2) &&
            b.charAt(i-2) == a.charAt(j-1)) {
          matrix[i][j] = Math.min(matrix[i][j], matrix[i-2][j-2] + 1); // transposition
        }
      }
    }
   
    return matrix[b.length][a.length];
  };

  if (typeof module === 'object' && 'exports' in module) {
    module.exports = getEditDistance;
  } else if (typeof window === 'object') {
    window['getEditDistance'] = getEditDistance;
  } else {
    return getEditDistance;
  }
})();
/*
vim: sw=2 ts=2 et ai si bg=dark
*/