... Cart" button, updated an array stored in the user's browser, and dynamically re-rendered the template's HTML cart elements without causing a single page reload. Here is the modular script I wrote to manage this: const MiniCart = { storageKey: 'mymedi_cart_items', items: [], init() { this.loadCart(); this.bindEvents(); this.render(); }, loadCart() { const stored = localStorage.getItem(this.storageKey); this.items = stored ? JSON.parse(stored) : []; }, saveCart() { localStorage.setItem(this.storageKey, JSON.stringify(this.items)); this.render(); }, bindEvents() { document.addEventListener('click', (e) => { const btn = e.target.closest('.add-to-cart-btn'); if (btn) { e.preventDefault(); const product ...