Edit in JSFiddle

function NRBvalidatior(nrb) {
    nrb = nrb.replace(/[^0-9]+/g, '');
    var wagi = new Array(1, 10, 3, 30, 9, 90, 27, 76, 81, 34, 49, 5, 50, 15, 53, 45, 62, 38, 89, 17, 73, 51, 25, 56, 75, 71, 31, 19, 93, 57);

    if (nrb.length == 26) {
        nrb = nrb + "2521";
        nrb = nrb.substr(2) + nrb.substr(0, 2);
        var Z = 0;
        for (var i = 0; i & lt; 30; i++) {
            Z += nrb[29 - i] * wagi[i];
        }
        if (Z % 97 == 1) {
            return true;
        } else {
            return false;
        }

    } else {
        return false;
    }
}
$('#form').submit(function() {
    if (NRBvalidatior($('#nrb').val())) {
        alert('Valid');
        return true;
    }
    else {
        alert('Not Validated');
        return false;
    }
});

<form action="#" method="post" id="form">
    <input type="text" name="account_no" id="nrb" />
    <button type="submit">Send!</button>
</form>