[nerv_]

как понял

function foo(a, b) {
    var one = a, two = b;
    return function (a, b) {
        return (one = a || one) + (two = b || two);
    }
}

var test = foo(1, 7);
alert(test());//8
alert(test(2, 3)); //5
alert(test())//5