If you have a pre-set number of things, use hidden form fields and set the values before submit.
If a dynamic number of things, dynamically create new form fields and set them before submit.
Of course, either of these require script on the client, and so should have a fallback for users with no script on sites that must meet ADA requirements.
If this post contains any code, I may or may not have tested it. It's probably just example code, so no getting knickers in a bunch over a typo, OK? If it doesn't have basic error checking in it, such as object detection or checking if objects are null before using them, put that in there. I'm giving examples, not typing up your whole app for you. You run code at your own risk.
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