Question

Below is Porters Stemming Algorithm for JavaScript which I have taken from here: http://tartarus.org/~martin/PorterStemmer/js.txt

I would like to be able to use the algorithm by simply calling:

var stemmed_word = porter_stemming_alg( "some_word_to_stem" );

Does anyone have any suggestions as to how I would incorporate this functionality into the code below??

Something along the lines of:

function porter_stemming_alg( word ){
    //...
    // algorithm goes here...
    //...
}

Any suggestions appreciated guys….

var stemmer = (function(){
var step2list = {
        "ational" : "ate",
        "tional" : "tion",
        "enci" : "ence",
        "anci" : "ance",
        "izer" : "ize",
        "bli" : "ble",
        "alli" : "al",
        "entli" : "ent",
        "eli" : "e",
        "ousli" : "ous",
        "ization" : "ize",
        "ation" : "ate",
        "ator" : "ate",
        "alism" : "al",
        "iveness" : "ive",
        "fulness" : "ful",
        "ousness" : "ous",
        "aliti" : "al",
        "iviti" : "ive",
        "biliti" : "ble",
        "logi" : "log"
    },

    step3list = {
        "icate" : "ic",
        "ative" : "",
        "alize" : "al",
        "iciti" : "ic",
        "ical" : "ic",
        "ful" : "",
        "ness" : ""
    },

    c = "[^aeiou]",          // consonant
    v = "[aeiouy]",          // vowel
    C = c + "[^aeiouy]*",    // consonant sequence
    V = v + "[aeiou]*",      // vowel sequence

    mgr0 = "^(" + C + ")?" + V + C,               // [C]VC... is m>0
    meq1 = "^(" + C + ")?" + V + C + "(" + V + ")?$",  // [C]VC[V] is m=1
    mgr1 = "^(" + C + ")?" + V + C + V + C,       // [C]VCVC... is m>1
    s_v = "^(" + C + ")?" + v;                   // vowel in stem

return function (w) {
    var     stem,
        suffix,
        firstch,
        re,
        re2,
        re3,
        re4,
        origword = w;

    if (w.length < 3) { return w; }

    firstch = w.substr(0,1);
    if (firstch == "y") {
        w = firstch.toUpperCase() + w.substr(1);
    }

    // Step 1a
    re = /^(.+?)(ss|i)es$/;
    re2 = /^(.+?)([^s])s$/;

    if (re.test(w)) { w = w.replace(re,"$1$2"); }
    else if (re2.test(w)) { w = w.replace(re2,"$1$2"); }

    // Step 1b
    re = /^(.+?)eed$/;
    re2 = /^(.+?)(ed|ing)$/;
    if (re.test(w)) {
        var fp = re.exec(w);
        re = new RegExp(mgr0);
        if (re.test(fp[1])) {
            re = /.$/;
            w = w.replace(re,"");
        }
    } else if (re2.test(w)) {
        var fp = re2.exec(w);
        stem = fp[1];
        re2 = new RegExp(s_v);
        if (re2.test(stem)) {
            w = stem;
            re2 = /(at|bl|iz)$/;
            re3 = new RegExp("([^aeiouylsz])\\1$");
            re4 = new RegExp("^" + C + v + "[^aeiouwxy]$");
            if (re2.test(w)) {  w = w + "e"; }
            else if (re3.test(w)) { re = /.$/; w = w.replace(re,""); }
            else if (re4.test(w)) { w = w + "e"; }
        }
    }

    // Step 1c
    re = /^(.+?)y$/;
    if (re.test(w)) {
        var fp = re.exec(w);
        stem = fp[1];
        re = new RegExp(s_v);
        if (re.test(stem)) { w = stem + "i"; }
    }

    // Step 2
    re = /^(.+?)(ational|tional|enci|anci|izer|bli|alli|entli|eli|ousli|ization|ation|ator|alism|iveness|fulness|ousness|aliti|iviti|biliti|logi)$/;
    if (re.test(w)) {
        var fp = re.exec(w);
        stem = fp[1];
        suffix = fp[2];
        re = new RegExp(mgr0);
        if (re.test(stem)) {
            w = stem + step2list[suffix];
        }
    }

    // Step 3
    re = /^(.+?)(icate|ative|alize|iciti|ical|ful|ness)$/;
    if (re.test(w)) {
        var fp = re.exec(w);
        stem = fp[1];
        suffix = fp[2];
        re = new RegExp(mgr0);
        if (re.test(stem)) {
            w = stem + step3list[suffix];
        }
    }

    // Step 4
    re = /^(.+?)(al|ance|ence|er|ic|able|ible|ant|ement|ment|ent|ou|ism|ate|iti|ous|ive|ize)$/;
    re2 = /^(.+?)(s|t)(ion)$/;
    if (re.test(w)) {
        var fp = re.exec(w);
        stem = fp[1];
        re = new RegExp(mgr1);
        if (re.test(stem)) {
            w = stem;
        }
    } else if (re2.test(w)) {
        var fp = re2.exec(w);
        stem = fp[1] + fp[2];
        re2 = new RegExp(mgr1);
        if (re2.test(stem)) {
            w = stem;
        }
    }

    // Step 5
    re = /^(.+?)e$/;
    if (re.test(w)) {
        var fp = re.exec(w);
        stem = fp[1];
        re = new RegExp(mgr1);
        re2 = new RegExp(meq1);
        re3 = new RegExp("^" + C + v + "[^aeiouwxy]$");
        if (re.test(stem) || (re2.test(stem) && !(re3.test(stem)))) {
            w = stem;
        }
    }

    re = /ll$/;
    re2 = new RegExp(mgr1);
    if (re.test(w) && re2.test(w)) {
        re = /.$/;
        w = w.replace(re,"");
    }

    // and turn initial Y back to y

    if (firstch == "y") {
        w = firstch.toLowerCase() + w.substr(1);
    }

    return w;
}
})();

Answer 1

That’s already a function. You can call it with stemmer( "some_word_to_stem" ). If you want to change the function’s name either edit the first line to var porter_stemming_alg = ... or add var porter_stemming_alg = stemmer; at the end.