Product Quantity Counter & Add-to-Cart Button

I need a straightforward quantity counter (with “+ / –” controls) placed right beside an Add-to-Cart button so shoppers can pick any amount and send that exact number straight into the cart in one click. The feature has to look native to the site’s current style, work smoothly on desktop and mobile, and update the cart totals instantly without a full page reload.

Please code it cleanly, keep the files organised, and document the key steps so I can maintain it later. If you have a preferred JavaScript framework or a proven Shopify / WooCommerce snippet that does this elegantly, feel free to suggest it—my main goal is a snappy user experience and clean, reusable code.

Deliverables
• Responsive quantity counter with increment / decrement
• Add-to-Cart action that passes the chosen quantity and refreshes totals via AJAX (or equivalent)
• Brief implementation notes so I can replicate the setup on additional products or pages

I’m ready to start as soon as you can confirm the approach and timeline.