Variable array for alternating outcomes (javascript) : Hi im making a small javascript drinking game just for abit of fun n to learn certain aspects of javascript, iv looked over the code i have wrote n cant see why it doesnt work

Im trying to show a random array taken from the 2 variable arrays and alternate between them both, i dnt care for storage as the game wont need to be reloaded n there is no links to other pages so that is not a problem.

Please can people give me some pointers on what im doing wrong

    <!DOCTYPE HTML5>

    <html>

    <head>

    <script>

    var boy = ["have a shot","item 2","item 3"];
    var girl = ["have a shot","item 2","item 3"];
    var selector = 1;

    function rbg()

    if (selector == 1)
    {
    document.getElementById("ppp").innerHTML = boy [Math.floor(Math.random() * boy.length)];
    selector = 2;
    }

    else if (selector == 2)
    {
    document.getElementById("ppp").innerHTML = girl [Math.floor(Math.random() * girl.length)];
    selector = 0;
    }

    else
    {
    document.getElementById("ppp".innerHTML = "have a shot each";
    selector = 1;
    }

    </script>

    <title>Home</title>

    </head>

    <body>

    <div id="random" onclick="rbg()">Random</div>

     <p id="ppp">outcome</p>

    </body>

    </html>