Capturing javascript updates with selenium

You can find a new/added element in a loop. It could look like this in Java:

WebElement element = driver.findElement(By.id("theId"));
int count = 0;

while (element != null && count < 60) {

    // get the element again
    element = driver.findElement(By.id("theId"));

    // do something with the element...
    log(element.text());

    // wait one second
    Thread.sleep(1000);

    // increment a count if you want to eventually escape this loop, in case you never find your elment
    count++;
}

If that doesn't work for your purpose, you can get the full source code of the page and parse it for whatever information you are looking for.

String pageSource = driver.getPageSource();

You can do that in a loop like above, and keep trying until you reach a timeout or find the updated info.