spelling-corrector/src/spell.js

nodeJs Spelling Corrector version for Norvig's spelling corrector.

var HashMap = require('hashmap');
var fs = require('fs');

var spellCorrector = function() {
    this.nWords = new HashMap();
    this.alphabet = "abcdefghijklmnopqrstuvwxyz".split("");
}

spellCorrector.prototype.loadDictionary = function(dictPath) {
    dictPath = dictPath || __dirname + '/big.txt';
    var file = fs.readFileSync(dictPath).toString().toLowerCase();
    var regex = /[a-z]+/g;
    var match, word;
    while ((match = regex.exec(file))) {
        word = match[0];
        var newCount = 1;
        if (this.nWords.has(word)) {
            newCount = newCount + this.nWords.get(word);
        }
        this.nWords.set(word, newCount);
    }
}

spellCorrector.prototype.getEdits = function(word) {
    var result = [];
    for (var i = 0; i < word.length; i++) result.push(word.slice(0, i) + word.slice(i + 1));
    for (var i = 0; i < word.length - 1; i++) result.push(word.slice(0, i) + word.slice(i + 1, i + 2) + word.slice(i, i + 1) + word.slice(i + 2));
    for (var i = 0; i < word.length; i++)
        for (var j = 0; j < this.alphabet.length; j++) result.push(word.slice(0, i) + this.alphabet[j] + word.slice(i + 1));
    for (var i = 0; i <= word.length; i++)
        for (var j = 0; j < this.alphabet.length; j++) result.push(word.slice(0, i) + this.alphabet[j] + word.slice(i));
    return result;
}

spellCorrector.prototype.correct = function(word) {
    if (this.nWords.has(word)) {
        return word;
    }
    var suggestions = this.getEdits(word);
    var candidates = new HashMap();
    suggestions.forEach(function(curWord) {
        if (this.nWords.has(curWord)) {
            candidates.set(this.nWords.get(curWord), curWord);
        }
    }.bind(this));

    if (candidates.count() > 0) {
        return bestCandidate(candidates);
    }

    suggestions.forEach(function(curWord) {
        var newSuggestions = this.getEdits(curWord);
        newSuggestions.forEach(function(newWord) {
            if (this.nWords.has(newWord)) {
                candidates.set(this.nWords.get(newWord), newWord);
            }
        }.bind(this));
    }.bind(this));
    return (candidates.count() > 0) ? bestCandidate(candidates) : word;
}

function bestCandidate(candidates) {
    var maxCount = 0;
    var word;
    candidates.forEach(function(value, key) {
        if (key > maxCount) {
            maxCount = key;
            word = value;
        }
    });
    return word;
}


module.exports.spellCorrector = spellCorrector;