HTML <aside> hidden Attribute

A hidden attribute on an <aside> tag.
The aside element (on the right side) is not visible.

<div style="display: flex;">
 <main>
   Art appreciation classes are<br />
   available in these cities: 
   <ul>
     <li>Amsterdam</li>
     <li>London</li>
     <li>Paris</li>
     <li>Rome</li>
     <li>Berlin</li>
     <li>New York</li>
     <li>Houston</li>
     <li>Los Angeles</li>
   </ul>
 </main>
 
 <aside hidden style="padding:80px;">
  <i>For the cheapest flights<br />
  please contact our travel<br />
  partner KLM.</i>
 </aside>
</div>

<aside hidden>

<aside hidden="hidden">

Clicking the button toggles A hidden attribute on the <aside> element.

<div style="display: flex;">
 <main>
   Art appreciation classes are<br />
   available in these cities: 
   <ul>
     <li>Amsterdam</li>
     <li>London</li>
     <li>Paris</li>
     <li>Rome</li>
     <li>Berlin</li>
     <li>New York</li>
     <li>Houston</li>
     <li>Los Angeles</li>
   </ul>
 </main>
 
 <aside style="margin:60px;padding:20px;background:aliceblue;" id="aside">
   <i>For the cheapest flights<br />
   please contact our travel<br />
   partner KLM.</i>
 </aside>
</div>

<br />
<button onclick="toggle(this);">Hide Aside</button>

<script>
  let toggle = button => {
    let element = document.getElementById("aside");
    let hidden = element.getAttribute("hidden");

    if (hidden) {
       element.removeAttribute("hidden");
       button.innerText = "Hide Aside";
    } else {
       element.setAttribute("hidden", "hidden");
       button.innerText = "Show Aside";
    }
  }
</script>

Code explanation

Here is when hidden support started for each browser:

Chrome	6.0	Sep 2010
Firefox	4.0	Mar 2011
IE/Edge	9.0	Mar 2011
Opera	11.1	Mar 2011
Safari	5.0	Jun 2010

• Our HTML aside Tag Reference
• Our HTML hidden Attribute Reference
• Our CSS display Property Reference