Types are cool, TypeScript is cool, and types with JSDocs are cool, https://dev.to/dakmor/type-safe-web-components-with-jsdoc-4i... and what's more, they're all cool with web components.
return html`
<h1>${this.format(this.title)}</h1>
<div
class="dot"
style=${`left: ${this.bar.x}px; top: ${this.bar.y}`}
title=${this.bar.title}
></div>
`;
const el = /** @type {TitleBar} */ (document.querySelector('title-bar'));
const el: TitleBar = document.querySelector('title-bar');