fuzzaldrin/vendor/stringscore.js

// MODIFIED BY NS/CJ - Don't extend the prototype of String
// MODIFIED BY CJ - Remove start_of_string_bonus

/*!
 * string_score.js: String Scoring Algorithm 0.1.10
 *
 * http://joshaven.com/string_score
 * https://github.com/joshaven/string_score
 *
 * Copyright (C) 2009-2011 Joshaven Potter <yourtech@gmail.com>
 * Special thanks to all of the contributors listed here https://github.com/joshaven/string_score
 * MIT license: http://www.opensource.org/licenses/mit-license.php
 *
 * Date: Tue Mar 1 2011
*/

/**
 * Scores a string against another string.
 *  'Hello World'.score('he');     //=> 0.5931818181818181
 *  'Hello World'.score('Hello');  //=> 0.7318181818181818
 */
module.exports = function(string, abbreviation) {
  // If the string is equal to the abbreviation, perfect match.
  if (string == abbreviation) {return 1;}

  var total_character_score = 0,
      abbreviation_length = abbreviation.length,
      string_length = string.length,
      start_of_string_bonus,
      abbreviation_score,
      final_score;

  // Walk through abbreviation and add up scores.
  for (var i = 0,
         character_score/* = 0*/,
         index_in_string/* = 0*/,
         c/* = ''*/,
         index_c_lowercase/* = 0*/,
         index_c_uppercase/* = 0*/,
         min_index/* = 0*/;
     i < abbreviation_length;
     ++i) {

    // Find the first case-insensitive match of a character.
    c = abbreviation.charAt(i);

    index_c_lowercase = string.indexOf(c.toLowerCase());
    index_c_uppercase = string.indexOf(c.toUpperCase());
    min_index = Math.min(index_c_lowercase, index_c_uppercase);
    index_in_string = (min_index > -1) ? min_index : Math.max(index_c_lowercase, index_c_uppercase);

    if (index_in_string === -1) {
      return 0;
    } else {
      character_score = 0.1;
    }

    // Set base score for matching 'c'.

    // Same case bonus.
    if (string[index_in_string] === c) {
      character_score += 0.1;
    }

    // Consecutive letter & start-of-string Bonus
    if (index_in_string === 0) {
      // Increase the score when matching first character of the remainder of the string
      character_score += 0.6;
      if (i === 0) {
        // If match is the first character of the string
        // & the first character of abbreviation, add a
        // start-of-string match bonus.
        // start_of_string_bonus = 1 //true;
      }
    }
    else {
      // Acronym Bonus
      // Weighing Logic: Typing the first character of an acronym is as if you
      // preceded it with two perfect character matches.
      if (string.charAt(index_in_string - 1) === ' ') {
        character_score += 0.8; // * Math.min(index_in_string, 5); // Cap bonus at 0.4 * 5
      }
    }

    // Left trim the already matched part of the string
    // (forces sequential matching).
    string = string.substring(index_in_string + 1, string_length);

    total_character_score += character_score;
  } // end of for loop

  // Uncomment to weigh smaller words higher.
  // return total_character_score / string_length;

  abbreviation_score = total_character_score / abbreviation_length;
  //percentage_of_matched_string = abbreviation_length / string_length;
  //word_score = abbreviation_score * percentage_of_matched_string;

  // Reduce penalty for longer strings.
  //final_score = (word_score + abbreviation_score) / 2;
  final_score = ((abbreviation_score * (abbreviation_length / string_length)) + abbreviation_score) / 2;

  if (start_of_string_bonus && (final_score + 0.15 < 1)) {
    final_score += 0.15;
  }

  return final_score;
};