django_ecommerce_mod5

I am fetching data and I have mapped the data to display it. Everything is fine but when I try to update the fetched data (which I have already stored in an array, just want to change it through other way , mentioned below) does not update.I have given the data below,I just want to change the 'quantity' attribute of each object respectively when I click the button but everytime I try to use the spread operator and give a comma and try to define the attribute of the mapped objects which is 'quantity' here, it doesnot update the quantity attribute and replaces the whole array.Can you please tell me how to write a onClick function which copies the whole array(using spread operator) and then update the quantity attribute.(the fetched data is stored in an array)