HTML popover Attribute

Modals have been an important part of websites for two decades. Stacking contents and using fetch to accomplish tasks are a great way to improve UX on both desktop and mobile. Unfortunately most developers don't know that the HTML and JavaScript specs have implemented a native modal system via the popover attribute -- let's check it out!

The HTML

Creating a native HTML modal consists of using the popovertarget attribute as the trigger and the popover attribute, paired with an id, to identify the content element:

<!-- 
  "popovertarget" attribute will map to "id" of popover contents
-->
<button popovertarget="popover-contents">Open popover</button>
<div id="popover-contents" popover>This is the contents of the popover</div>

Upon clicking the button, the popover will open. The popover, however, will not have a traditional background layer color so we'll need to implement that on our own with some CSS magic.

The CSS

Styling the contents of the popover content is pretty standard but we can use the browser stylesheet selector's pseudo-selector to style the "background" of the modal:

/* contents of the popover */
[popover] {
  background: lightblue;
  padding: 20px;
}

/* the dialog's "modal" background */
[popover]:-internal-popover-in-top-layer::backdrop {
  background: rgba(0, 0, 0, .5);  
}

:-internal-popover-in-top-layer::backdrop represents the "background" of the modal. Traditionally that UI has been an element with opacity such to show the stacking relationship.