CSS pseudo-class - :host-context()

CSS :host-context() pseudo-class selector allows you to style a custom element differently depending on where it is used in the DOM, based on the classes or attributes of its ancestor elements.

The :host-context() pseudo-class function has no effect when used outside a shadow DOM.

Syntax

:host-context(<compound-selector>) {
   /* ... */
}

The :host-context() is not supported by Firebox and Safari Browser.

CSS :host-context Example

The following example demonstrates how to use the :host-context() pseudo-class to style a custom element differently depending on its context in the DOM −

<html>
<head>
<style>
   div {
         background-color: yellow;
   }
</style>
</head>
<body>
   <div>
      <h3>Tutorialspoint CSS - <a href="#"><context-span>:host-context()</context-span></a></h3>
      <p>CSS <context-span>:host-context()</context-span> pseudo-class selector allows you to style a custom element differently depending on where it is used in the DOM, based on the classes or attributes of its ancestor elements.</p>
   </div>
      <script>
         class HostContext extends HTMLElement {
            constructor() {
               super();
               const shadowRoot = this.attachShadow({ mode: 'open' });
               const styleElement = document.createElement('style');
               styleElement.textContent = `
                  :host-context(div) {
                        color: blue;
                        background-color: violet;
                        border: 3px solid red;
                  }
                  :host-context(div)::after {
                        content: ":host-context()";
                  }`;
               shadowRoot.appendChild(styleElement);
            }
         }
      customElements.define('context-span', HostContext);
   </script>
</body>
</html>