soundex.js

function soundex (str) {
    // http://kevin.vanzonneveld.net
    // +   original by: Jonas Raoni Soares Silva (http://www.jsfromhell.com)
    // +    tweaked by: Jack
    // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   bugfixed by: Onno Marsman
    // +      input by: Brett Zamir (http://brett-zamir.me)
    // +   bugfixed by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   original by: Arnout Kazemier (http://www.3rd-Eden.com)
    // +    revised by: Rafał Kukawski (http://blog.kukawski.pl)
    // *     example 1: soundex('Kevin');
    // *     returns 1: 'K150'
    // *     example 2: soundex('Ellery');
    // *     returns 2: 'E460'
    // *     example 3: soundex('Euler');
    // *     returns 3: 'E460'
    str = (str + '').toUpperCase();
    if (!str) {
        return '';
    }
    var sdx = [0, 0, 0, 0],
        m = {
            B: 1,
            F: 1,
            P: 1,
            V: 1,
            C: 2,
            G: 2,
            J: 2,
            K: 2,
            Q: 2,
            S: 2,
            X: 2,
            Z: 2,
            D: 3,
            T: 3,
            L: 4,
            M: 5,
            N: 5,
            R: 6
        },
        i = 0,
        j, s = 0,
        c, p;

    while ((c = str.charAt(i++)) && s < 4) {
        if (j = m[c]) {
            if (j !== p) {
                sdx[s++] = p = j;
            }
        } else {
            s += i === 1;
            p = 0;
        }
    }

    sdx[0] = str.charAt(0);
    return sdx.join('');
}