akurath/client/utils/string.js

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define([
    'hr/hr'
], function (hr) {
    /**
     *  Scores a string against another string.
     *      score('Hello World', 'he');     //=> 0.5931818181818181
     *      score('Hello World', 'Hello');  //=> 0.7318181818181818
     */
    var score = function(string, word, fuzziness) {
        // If the string is equal to the word, perfect match.
        if (string == word) return 1;

        //if it's not a perfect match and is empty return 0
        if( word == "") return 0;

        var runningScore = 0,
                charScore,
                finalScore,
                lString = string.toLowerCase(),
                strLength = string.length,
                lWord = word.toLowerCase(),
                wordLength = word.length,
                idxOf,
                startAt = 0,
                fuzzies = 1,
                fuzzyFactor;
        
        // Cache fuzzyFactor for speed increase
        if (fuzziness) fuzzyFactor = 1 - fuzziness;

        // Walk through word and add up scores.
        // Code duplication occurs to prevent checking fuzziness inside for loop
        if (fuzziness) {
            for (var i = 0; i < wordLength; ++i) {

                // Find next first case-insensitive match of a character.
                idxOf = lString.indexOf(lWord[i], startAt);
                
                if (-1 === idxOf) {
                    fuzzies += fuzzyFactor;
                    continue;
                } else if (startAt === idxOf) {
                    // Consecutive letter & start-of-string Bonus
                    charScore = 0.7;
                } else {
                    charScore = 0.1;

                    // Acronym Bonus
                    // Weighing Logic: Typing the first character of an acronym is as if you
                    // preceded it with two perfect character matches.
                    if (string[idxOf - 1] === ' ') charScore += 0.8;
                }
                
                // Same case bonus.
                if (string[idxOf] === word[i]) charScore += 0.1; 
                
                // Update scores and startAt position for next round of indexOf
                runningScore += charScore;
                startAt = idxOf + 1;
            }
        } else {
            for (var i = 0; i < wordLength; ++i) {
            
                idxOf = lString.indexOf(lWord[i], startAt);
                
                if (-1 === idxOf) {
                    return 0;
                } else if (startAt === idxOf) {
                    charScore = 0.7;
                } else {
                    charScore = 0.1;
                    if (string[idxOf - 1] === ' ') charScore += 0.8;
                }

                if (string[idxOf] === word[i]) charScore += 0.1; 
                
                runningScore += charScore;
                startAt = idxOf + 1;
            }
        }

        // Reduce penalty for longer strings.
        finalScore = 0.5 * (runningScore / strLength  + runningScore / wordLength) / fuzzies;
        
        if ((lWord[0] === lString[0]) && (finalScore < 0.85)) {
            finalScore += 0.15;
        }
        
        return finalScore;
    };

    var endsWith = function(s, suffix) {
        return s.indexOf(suffix, s.length - suffix.length) !== -1;
    };

    return {
        'score': score,
        'endsWith': endsWith
    };
});