Introduction and Practice of Web Components and Shadow DOM

The article introduces Web Components, focusing on the Shadow DOM technique used in HTML5 video components and other elements like input and select.

It explains the three core technologies of Web Components:

• Template – generates DOM structures.

• Shadow DOM – provides CSS style isolation by creating an independent sandbox that does not interfere with other DOM elements, similar to Vue's scoped styles.

• Custom Elements – allows developers to define new elements by extending HTMLElement, inheriting standard HTML properties and APIs.

The piece then clarifies what Shadow DOM is: an isolated sandbox that naturally achieves CSS isolation.

Next, the article walks through a concrete component implementation (illustrated with images) and discusses how to make the component dynamic. It highlights the use of Web Components lifecycle callbacks, especially connectedCallback for initial mounting and attributeChangedCallback for reacting to attribute changes.

Event handling is compared to Vue's @click and React's onClick , with visual examples.

In the summary section, the characteristics of Web Components are listed, followed by several application scenarios:

• Component libraries – e.g., Taro v3 adopts Web Components.

• Cross‑platform development – a single Web Component can run on both web browsers and mini‑programs (e.g., via Taro runtime that simulates DOM/BOM APIs).

• Micro‑frontend architecture – Web Components satisfy technology‑agnostic, isolated, and independently developable requirements, making them suitable for micro‑frontend solutions.

The article concludes with a case study of the "Quark" component library built on Web Components, highlighting its capabilities such as a small bundle size (~20 KB), cross‑framework support (Vue, React, Angular, etc.), high‑quality components, on‑demand loading, comprehensive documentation, unit testing, TypeScript support, SSR compatibility, and theming.