Levenshtein Distance

levenstein.js

    /**
     * @license MIT 
     * Copyright 2019 @andrei-m
     * 
     * See original which this code is based on: 
     * https://gist.github.com/andrei-m/982927/0efdf215b00e5d34c90fdc354639f87ddc3bd0a5
     *
     * Basic modifications include using ES6 `const` and `let`.  Additionally
     * condenses if statement.  Changes are somewhat trivial overall :)
     *
     * 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.
     * 
     * @description
     * Computes a Levenshtein Distance.
     * 
     * This computes a Levenshtein Distance which most simply is a
     * distance in out-of-place letters, wrong letters, and missing 
     * letters.
     * 
     * @see https://en.wikipedia.org/wiki/Levenshtein_distance
     * @param {String} a The first word.  
     * @param {String} b The second word.
     * 
     * @returns {Number} The Levenshtein Distance between `a` and `b`.
     */
    const getLevenshteinDistance = (a, b) => {
        if (a.length == 0 || b.length == 0) {
            return 0;
        }
      
        const matrix = [];
      
        // Increment along the first column of each row.
        let i;
        for(i = 0; i <= b.length; i++){
          matrix[i] = [i];
        }
      
        // Increment each column in the first row.
        let 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
            }
          }
        }
      
        return matrix[b.length][a.length];
    }