function f() {
    a.clientTop && a.clientTop, a.clientTop === !0; // $ Alert
    a && a.clientTop;
    a.clientTop, a.clientTop;
    if (a) return a.clientTop && a.clientTop, a.clientTop === !0;
    if (b) return b && (b.clientTop, b.clientTop && b.clientTop), null;
}