// define these as global variables
// or else you will get an error in ECMAScript 5/Strict mode
var divWidth = 0,
    divHeight = 0,
    timer,
    queue = [];

function growDiv() {

    // empty the queue
    queue.length = 0;

    // queue up some elements to animate
    queue.push(div1, div2);

    // animate the next element, if any
    runQueue();

}

function runQueue() {
    if (queue.length > 0) {
        timer = setInterval(function () {
            animate( queue.shift() );
        }, 20);
    }
}

function animate(div) {
    divWidth += 5;
    divHeight += 5;
    S(div).width = divWidth;
    S(div).height = divHeight;
    if (divWidth >= 100) {
        clearInterval(timer);
        divWidth = 0;
        divHeight = 0;
        runQueue();
    }
}