Javascript String soundex(p)

//<![CDATA[/*from  www . ja  va 2 s.  co  m*/
//@ http://jsfromhell.com/string/soundex [v1.0]
String.prototype.soundex = function(p){ //v1.0
    var i, j, r, p = isNaN(p) ? 4 : p > 10 ? 10 : p < 4 ? 4 : p,
    m = {BFPV: 1, CGJKQSXZ: 2, DT: 3, L: 4, MN: 5, R: 6},
    r = (s = this.toUpperCase().replace(/[^A-Z]/g, "").split("")).splice(0, 1);
    for(i in s)
        for(j in m)
            if(j.indexOf(s[i]) + 1 && r[r.length-1] != m[j] && r.push(m[j]))
                break;
    return r.length > p && (r.length = p), r.join("") + (new Array(p - r.length + 1)).join("0");
};
//]]>