The editable quantity TextField rendered for each cart item allows the user to update the quantity for each product they are buying, and sets a minimum allowed value of 1.
mern-marketplace/client/cart/CartItems.js:
Quantity: <TextField value={item.quantity} onChange={this.handleChange(i)} type="number" inputProps={{ min:1 }} InputLabelProps={{ shrink: true, }} />
When the user updates this value, the handleChange method is called to enforce the minimum value validation, update the cartItems in state, and update the cart in localStorage using the helper method.
mern-marketplace/client/cart/CartItems.js:
handleChange = index => event => { let cartItems = this.state.cartItems if(event.target.value == 0){ cartItems[index].quantity ...