HTML <aside> id Attribute

The id attribute on an <aside> tag assigns an identifier to the aside element. The identifier must be unique across the page.

Example

#

An id attribute on an <aside> element.

Art appreciation classes are
available in these cities:
  • Amsterdam
  • London
  • Paris
  • Rome
  • Berlin
  • New York
  • Houston
  • Los Angeles
<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 id="vangogh-aside"
        style="margin:80px;padding:20px;border-left:2px solid red;">
  <i>For the cheapest flights<br />
  please contact our travel<br />
  partner KLM.</i>
 </aside>
</div>

Using id

The id attribute assigns an identifier to the <aside> element.

The identifier must be unique across the page.

The id allows programmatic access to the <aside> element.

Tip:  id is a global attribute that can be applied to any HTML element.


Syntax

<aside id="identifier" />

Values

#

Value Description
identifier A unique alphanumeric string. The id value must begin with a letter ([aside-Zaside-z]) and may be followed by any number of letters, digits ([0-9]), hyphens (-), underscores (_), colons (:), and periods (.).

More Examples

An <aside> with a unique id value.
Clicking the button displays the content of the aside.

Art appreciation classes are
available in these cities:
  • Amsterdam
  • London
  • Paris
  • Rome
  • Berlin
  • New York
  • Houston
  • Los Angeles

<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 id="myaside"
        style="margin:80px;padding:20px;border-left:2px solid red;">
   <i>For the cheapest flights<br />
   please contact our travel<br />
   partner KLM.</i>
 </aside>
</div>

<br/>
<button onclick="show();">Show aside</button>

<script>
  let show  = () => {
    let element = document.getElementById("myaside");
    alert("Aside content = " + element.innerHTML);
  }
</script>

Code explanation

The id attribute assigns a unique identifier to the aside.

Clicking the button calls JavaScript which locates the <aside> element using the id.

Finally, the content of the aside element is displayed in an alert box.


Browser support

Here is when id 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

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