title: Local Storage is not shared between pages
body: <p>I have an epub3 book with 2 pages as well as a Table of Contents Page. I am viewing this book in Apple's Books, their inbuilt epub3 reader, on Mac OSX. The two pages appear side by side. The first page is as follows:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;html xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops"&gt;
      &lt;head&gt;
          &lt;meta charset="utf-8" /&gt;
          &lt;meta name="viewport" content="width=500, height=600"/&gt;
      &lt;/head&gt;
      &lt;body&gt;
  
  &lt;p id="result"&gt;&lt;/p&gt;
  
  &lt;script&gt;
  //&lt;![CDATA[
    var current_page = "1";
    var other_page = "2";
  
    var t = 0;
  
    setInterval(function() {
  
      var d = new Date();
      var storage = localStorage; 
  
      storage.setItem("t"+ current_page, d.toLocaleString());
  
      document.getElementById("result").innerHTML = storage.getItem("t"+ current_page) +" "+storage.getItem("t"+ other_page);    
    }, 1000);
  
  //]]&gt;
  &lt;/script&gt;
  
      &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>and the only thing different in my second page is:</p>
  
  <pre><code>  var current_page = "2";
    var other_page = "1";
  </code></pre>
  
  <p>So every second, Page 1 saves the current time to Local Storage as <code>t1</code>, and Page 2 does the same for the value <code>t2</code>. At the same time, both pages are reading both <code>t1</code> and <code>t2</code> from Local Storage, before their values are displayed to screen. However in ibooks, Page 1 only manages to display the current value for <code>t2</code> when the page is reloaded - like when I flip to the Table of Contents and then back to Page 1 and 2 again. With something similar happening for Page 2 with regard to <code>t1</code>. </p>
  
  <p>So at time 21:10:00, Page 1 might display: </p>
  
  <p>08/09/19, 21:09:18       08/09/19, 21:08:58 </p>
  
  <p>and Page 2:</p>
  
  <p>08/09/19, 21:09:22       08/09/19, 21:08:01</p>
  
  <p>I also tried using Session Data but Page 1 can't ever read <code>t2</code> and Page 2 can't read <code>t1</code>. So, this would be displayed instead:</p>
  
  <p>08/09/19, 21:09:18       null</p>
  
  <p>I can think of several applications where it would be very useful for Pages to communicate with each other. </p>
  
  <p>For example, if a video is playing on one page, it would be useful to stop it if a video on another page is started. This would normally be done using Session Storage. This is related to my own use case and the reason I started exploring this problem.</p>
  
  <p>Likewise, if the user is asked on Page 1 to enters the name of the main character of the story, then that entry should appear immediately on Page 2 once it is entered.</p>
  
  <p>Is there any other way for Pages to communicate with each other in epub3 other than Local or Session Storage?</p>