Understanding Web Components: Features, Lifecycle, and Integration with Modern Frameworks

Web Components are a set of native browser technologies that let developers create reusable, encapsulated custom elements without loading external frameworks, enabling component‑based development across different libraries.

Key features include:

Custom Elements : define new HTML tags via JavaScript classes and register them with window.customElements.define .

Shadow DOM : attach an isolated DOM tree to an element using this.attachShadow({mode: "open"}) , providing style and script encapsulation.

HTML Templates : reuse markup with <template> and <slot> for content projection.

The component lifecycle methods ( connectedCallback , disconnectedCallback , attributeChangedCallback , adoptedCallback ) allow developers to react to DOM changes and attribute updates.

Example of a custom button :

class CustomButton extends HTMLElement {
  constructor() {
    super();
    const button = document.createElement("button");
    button.innerText = this.getAttribute("name") || "custom button";
    this.appendChild(button);
  }
}
window.customElements.define("custom-button", CustomButton);

Integration with frameworks :

React: wrap a Web Component in JSX and pass attributes; the component can update its shadow DOM based on prop changes.

Vue: use defineCustomElement to create a Vue‑based custom element that can be consumed anywhere.

A practical plugin system is demonstrated where a host application loads a Web Component plugin at runtime, injects its CSS, and executes bundled JavaScript inside the component’s shadow root, achieving script and style isolation.

Micro‑frontend examples show how multiple independent Web Components (React, Vue, future Flutter) can be loaded into a single page using tabs, each encapsulated in its own shadow DOM.

Comparison with frameworks :

Advantages: no extra runtime, lightweight, easy to combine with any framework, low learning curve.

Drawbacks: limited browser support without polyfills, cannot unregister a custom element, manual state handling, and style sharing across components can be cumbersome.

Extensions such as Lit and Omi provide higher‑level APIs for building Web Components with reactive state, scoped styles, and declarative templates.

References: MDN Web Components, Shadow DOM guide, Lit documentation, Omi repository.