popstate event handler seems not to work
<p>I'm having a problem with a 'popstate' event handler, this is my code:</p>

<pre><code>window.addEventListener("popstate", function (event){
    if (event.state) {
        alert('abc')
    }
});

// The data object is arbitrary and is passed with the popstate event.
var dataObject = {
    createdAt: '2011-10-10',
    author: 'donnamoss'
};

var url = '/posts/new-url';
history.pushState(dataObject, document.title, url);
</code></pre>

<p>I expected this code will pop up an alert box when it's executed but, nothing happens. </p>

<p>Is there anything wrong here?</p>

<p>Thank you.</p>
