quicksilver.js

// qs_score - Quicksilver Score
// 
// A port of the Quicksilver string ranking algorithm
// 
// "hello world".score("axl") //=> 0.0
// "hello world".score("ow") //=> 0.6
// "hello world".score("hello world") //=> 1.0
//
// Tested in Firefox 2 and Safari 3
//
// The Quicksilver code is available here
// http://code.google.com/p/blacktree-alchemy/
// http://blacktree-alchemy.googlecode.com/svn/trunk/Crucible/Code/NSString+BLTRRanking.m
//
// The MIT License
// 
// Copyright (c) 2008 Lachie Cox
// 
// 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.


String.prototype.score = function(abbreviation) {

  if(abbreviation.length === 0) { return 0.9; }
  if(abbreviation.length > this.length) { return 0.0; }
  
  var i, sub_abbreviation, index, next_string, next_abbreviation, remaining_score, score, j, c;

  for (i = abbreviation.length; i > 0; --i) {
  
    sub_abbreviation = abbreviation.substring(0,i);
    index            = this.indexOf(sub_abbreviation);

    if(index < 0) { continue; }
    if(index + abbreviation.length > this.length ) { continue; }

    next_string       = this.substring(index+sub_abbreviation.length);
    next_abbreviation = null;

    if(i >= abbreviation.length) {
      next_abbreviation = '';
    }
    else {
      next_abbreviation = abbreviation.substring(i);
    }
 
    remaining_score   = next_string.score(next_abbreviation,index);
 
    if (remaining_score > 0) {
    
      score = this.length-next_string.length;

      if(index !== 0) {
      
        j = 0;

        c = this.charCodeAt(index-1);
        if(c==32 || c == 9) {
          for(j=(index-2); j >= 0; --j) {
            c = this.charCodeAt(j);
            score -= ((c == 32 || c == 9) ? 1 : 0.15);
          }

        } else {
          score -= index;
        }
        
      }
   
      score += remaining_score * next_string.length;
      score /= this.length;
      return score;
      
    }
  }
  return 0.0;
};