title: How to get the text inside the alert box?
body: <p>I have some html pages, and they are <code>alert(some_value)</code>. </p>
  
  <p>I want to use Javascript to get the text inside the alert box. I want something just like <code>document.querySeletor</code>, which I usually use that to get the element in the page.</p>
  
  <p>But I can't find a proper api to achieve that, so could any one give me some suggestions about that?</p>