validateSAID.js

function validateSAID(idnum) {
    idnum = idnum.toString().replace(" ", "");
    r = /^\d{10}[0-1]\d{2}$/;
    if (!r.test(idnum)) return false;
    n = idnum;
    p1 = parseInt(n[0]) + parseInt(n[2]) + parseInt(n[4]) + parseInt(n[6]) + parseInt(n[8]) + parseInt(n[10]);
    p2 = (parseInt(n[1] + n[3] + n[5] + n[7] + n[9] + n[11]) * 2).toString();
    p3 = 0;
    for (i = 0; i < p2.length; i++) {
        p3 += parseInt(p2[i]);
    }
    check = 10 - (p1 + p3).toString()[(p1 + p3).toString().length - 1];
    check_char = check > 9 ? check.toString()[1] : check.toString();
    if (check_char != idnum[12]) return false;
    return true;
}

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via comments on http://geekswithblogs.net/willemf/archive/2005/10/30/58561.aspx