liquidmetal.js

/*
 * LiquidMetal, version: 0.1 (2009-02-05)
 *
 * A mimetic poly-alloy of Quicksilver's scoring algorithm, essentially
 * LiquidMetal.
 *
 * For usage and examples, visit:
 * http://github.com/rmm5t/liquidmetal
 *
 * Licensed under the MIT:
 * http://www.opensource.org/licenses/mit-license.php
 *
 * Copyright (c) 2009, Ryan McGeary (ryanonjavascript -[at]- mcgeary [*dot*] org)
 */
var LiquidMetal = function() {
  var SCORE_NO_MATCH = 0.0;
  var SCORE_MATCH = 1.0;
  var SCORE_TRAILING = 0.8;
  var SCORE_TRAILING_BUT_STARTED = 0.9;
  var SCORE_BUFFER = 0.85;

  return {
    score: function(string, abbreviation) {
      // Short circuits
      if (abbreviation.length == 0) return SCORE_TRAILING;
      if (abbreviation.length > string.length) return SCORE_NO_MATCH;

      var scores = this.buildScoreArray(string, abbreviation);

      var sum = 0.0;
      for (var i in scores) {
        sum += scores[i];
      }

      return (sum / scores.length);
    },

    buildScoreArray: function(string, abbreviation) {
      var scores = new Array(string.length);
      var lower = string.toLowerCase();
      var chars = abbreviation.toLowerCase().split("");

      var lastIndex = -1;
      var started = false;
      for (var i in chars) {
        var c = chars[i];
        var index = lower.indexOf(c, lastIndex+1);
        if (index < 0) return fillArray(scores, SCORE_NO_MATCH);
        if (index == 0) started = true;

        if (isNewWord(string, index)) {
          scores[index-1] = 1;
          fillArray(scores, SCORE_BUFFER, lastIndex+1, index-1);
        }
        else if (isUpperCase(string, index)) {
          fillArray(scores, SCORE_BUFFER, lastIndex+1, index);
        }
        else {
          fillArray(scores, SCORE_NO_MATCH, lastIndex+1, index);
        }

        scores[index] = SCORE_MATCH;
        lastIndex = index;
      }

      var trailingScore = started ? SCORE_TRAILING_BUT_STARTED : SCORE_TRAILING;
      fillArray(scores, trailingScore, lastIndex+1);
      return scores;
    }
  };

  function isUpperCase(string, index) {
    var c = string.charAt(index);
    return ("A" <= c && c <= "Z");
  }

   function isNewWord(string, index) {
    var c = string.charAt(index-1);
    return (c == " " || c == "\t");
  }

  function fillArray(array, value, from, to) {
    from = Math.max(from || 0, 0);
    to = Math.min(to || array.length, array.length);
    for (var i = from; i < to; i++) { array[i] = value; }
    return array;
  }
}();