Like button, unique like, no sign-in, display count


how could it be possible to have a button to like an item (with only the possibility to like an item one time), without having to sign users in ?

Then I would also display the number of likes given to the item.


Not really.
You could record the likes in a User Specific boolean column, and then use the state of that to prevent further likes, but it would not persist across sessions. So the next time a user came back (or even if they just refresh the page) the state of the boolean would be reset and they’d be able to add a second like.

Assuming that you are recording likes in a User Specific column, you would also need an action to increment a (non-user specific) global counter. This is because you cannot rollup the values in user specific columns across all users.