This is an Alibaba interview question with many methods. Communication can be achieved by using the storage event of localstorage; shadredworker can also solve the problem; and websocket can also be used.

If you can control the ab page and even decide the URL: sharedworker / localstorage / sessionstorage can be used

<ul>
<li><a href="/song-1" target="player">song-1</a></li>
<li><a href="/song-2" target="player">song-2</a></li>
<li><a href="/song-3" target="player">song-3</a></li>
</ul>

The attribute target="framename" means opening the link in the specified frame (page).
Can be achieved:
When you click to add items to the shopping cart, if the shopping cart page is already open, only refresh the page instead of opening a new one Shopping cart page.
When you click to play a song, if the player page is already open, only the page will be refreshed instead of opening a new player page.

Here’s an idea:
The browser opens two web pages with the same domain name at the same time. Their localStorage是共享的，不仅如此，他们之间的localStorage值改变也是可以监听的。同域的a和b两个页面，a页面发生localStorage.set('abc', 123) and b pages can monitor changes in the following ways:

window.addEventListener("storage", function(e){  
  console.log('key:', e.key); // "abc"
  console.log('oldValue:', e.oldValue); // null
  console.log('newValue:', e.newValue); // 123
});