Why should you care?

Design systems can ship that works on any site.

See it live — copy this example

Paste into an HTML file or the browser console (F12). Use Run below when the live editor is available.

class HelloBox extends HTMLElement {
  connectedCallback() {
    this.textContent = "Hello from " + this.tagName;
  }
}
customElements.define("hello-box", HelloBox);
// <hello-box></hello-box>

Run Example »

Edit the code below and click Run to see the result in Toolliyo’s live editor.

What happened?

• connectedCallback runs when element enters the page.
• define registers the tag name.

Practice next

1. Define hello-box and use in HTML.
2. build connectedCallback.
3. Add shadow DOM for scoped CSS.
4. Pass attribute value to custom element via observedAttributes.
5. Clone template content inside shadow root.

Remember

customElements.define Shadow DOM for styles Native reusable tags

ScriptVerse design system

Shared web component works in legacy jQuery pages and new React shells alike.

Outcome: Web components ship reusable UI across heterogeneous ScriptVerse products.