JavaScript Store Popup Development

I want a lightweight, reusable JavaScript popup that I can drop into any page of my online store with a single script tag. The component must be written in clean, modern ES6, free of external dependencies, and easy for me to configure from a single JSON-style options object (text, images, timing, triggers, colours, width, etc.).

Core behaviour
• Render automatically after the script loads, attach to the DOM, and respect whatever trigger I set—instant, timed delay, or manual call from a button/link.
• Fade-in / fade-out transitions handled in pure CSS so I can style or override them later.
• Include built-in hooks for “close”, “submit”, or any custom CTA I define, returning events so I can tie them into Google Analytics or my e-mail service.

Code & hand-off
• One self-contained .js file and an optional .css file.
• Well-commented source plus a minified production build.
• A short README that shows how to initialise the popup, list all configuration options, and demonstrates two example use cases (email capture and discount notice).

Acceptance
I’ll drop the files into a staging page; the popup must load without console errors in the latest Chrome, Safari, Firefox, and Edge, and pass Google Lighthouse with no accessibility warnings.