@lit-labs/observers

@lit-labs/observers

A set of reactive controllers that facilitate using the platform observer objects, including:

• MutationObserver
• ResizeObserver
• IntersectionObserver
• PerformanceObserver

[!WARNING]

This package is part of Lit Labs. It is published in order to get feedback on the design and may receive breaking changes or stop being supported.

Please read our Lit Labs documentation before using this library in production.

Give feedback: https://github.com/lit/lit/discussions/3355

Overview

The modern web platform provides a number of observer helpers that can be used to detect changes to which web applications may want to react. By managing one of these observers with a reactive controller, changes can be easily integrated into the Lit reactive update lifecycle. The controller can also help manage observer cleanup and rendering in response to changes.

Installation

From inside your project folder, run:

$ npm install @lit-labs/observers

Usage

Here's an example:

import {MutationController} from '@lit-labs/observers/mutation-controller.js';
// ...

class MyElement extends LitElement {
  private _observer = new MutationController(this, {
    config: {attributes: true},
  });

  render() {
    return html` ${this._observer.value ? `Attributes set!` : ``} `;
  }
}

Contributing

Please see CONTRIBUTING.md.