What about asynchronous scripts?

Everything that we have looked at so far has been a synchronous piece of JavaScript. However, what if we wanted to perform some asynchronous JavaScript calls as a part of our test? Well, we can do this. The JavascriptExecutor also has a method called executeAsyncScript(). This will allow you to run some JavaScript that does not respond instantly. Let's have a look at some examples.

First of all, we are going to write a very simple bit of JavaScript that will wait for 25 seconds before triggering a callback, as follows:

@Test
private void javascriptExample() {
driver.manage().timeouts().setScriptTimeout(60, 
    TimeUnit.SECONDS);
driver.executeAsyncScript("var callback =  
    arguments[arguments.length - 1]; 
    window.setTimeout(callback, 25000);");
driver.get("http://www.google.com");
}

Note that we defined a JavaScript variable named callback, which uses a script argument that we have not set. For asynchronous scripts, Selenium needs to have a callback...