Adjust the "quantity" field in the cart forms on the product pages.
Change the step increment from 1 to 10, starting at 10.
This means the quantities available should be 10, 20, 30, and so on, instead of the default 1, 2, 3, etc.
Additional Task (Optional):
If the user selects a quantity of 70, display a plain JavaScript alert with the message "Great Choice!".
NB: There are many solutions for this problem, but I've chosen to override a specific template and put a javascript code, thus I'll not modify many templates either.
I believe that the solution you wanted to achieve should only be implemented in your end application and not in the Sylius project template, as this is a very specific case 🖖🏻
In that pull request I have:
Fork and Clone the Sylius Standard Repository
Modify Cart Quantity Field:
Change the step increment from 1 to 10, starting at 10.
This means the quantities available should be 10, 20, 30, and so on, instead of the default 1, 2, 3, etc.
NB: There are many solutions for this problem, but I've chosen to override a specific template and put a javascript code, thus I'll not modify many templates either.