The :host
CSS pseudo-class selects the shadow host of the shadow DOM containing the CSS it is used inside — in other words, this allows you select a custom element from inside its shadow DOM.
Note: This has no effect when used outside a shadow DOM.
/* Selects a shadow root host */ :host { font-weight: bold; }
Syntax not found in DB!
The following snippets are taken from our host-selectors example (see it live also).
In this example we have a simple custom element — <context-span>
— that you can wrap around text:
<h1>Host selectors <a href="#"><context-span>example</context-span></a></h1>
Inside the element's constructor, we create style
and span
elements, fill the span
with the content of the custom element, and fill the style
element with some CSS rules:
let style = document.createElement('style'); let span = document.createElement('span'); span.textContent = this.textContent; const shadowRoot = this.attachShadow({mode: 'open'}); shadowRoot.appendChild(style); shadowRoot.appendChild(span); style.textContent = 'span:hover { text-decoration: underline; }' + ':host-context(h1) { font-style: italic; }' + ':host-context(h1):after { content: " - no links in headers!" }' + ':host-context(article, aside) { color: gray; }' + ':host(.footer) { color : red; }' + ':host { background: rgba(0,0,0,0.1); padding: 2px 5px; }';
The :host { background: rgba(0,0,0,0.1); padding: 2px 5px; }
rule styles all instances of the <context-span>
element (the shadow host in this instance) in the document.
Specification | Status | Comment |
---|---|---|
CSS Scoping Module Level 1 The definition of ':host' in that specification. | Working Draft | Initial definition. |
Desktop | ||||||
---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | |
Basic support | Yes | No
|
63
|
No | Yes | Yes |
Mobile | |||||||
---|---|---|---|---|---|---|---|
Android webview | Chrome for Android | Edge Mobile | Firefox for Android | Opera for Android | iOS Safari | Samsung Internet | |
Basic support | Yes | Yes | No
|
63
|
Yes | Yes | Yes |
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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/CSS/:host