Newbie to Javascript: how to avoid sending data that have not changed?

I'm a newbie Javascript learner and I want to post serialized data of input checkboxes. The data are sent to the server in order to update the corresponding field in SQL table. Later, the user can review the selections he made the first time and deselect some checkboxes. If I understand well, only the selected items will be sent, not the unselected ones. How can I send all the info I need to update the newly selected items and the newly unselected ones?

The only solution I found is to make 2 updates: the first resets to 0 all the rows and the second one sets to 1 the selected items (newly selected or not) that are sent in the serialized array. Is there a more optimal way to do the job? Ideally, I would update only the data that have changed. Is it possible?

Regards, Patrick