Angular Js Retain Original Information and add new values to said information

I have an endpoint that carries out a PUT, the endpoint is designed so when you add a new user it will remove the users you have not specified in the JSON body. So if I send a request containing 1 and there are both 1 and 2, it will keep the 1 and remove the 2. However, due to that it has caused an issue in my GUI. I have drop down lists which use this information and I would like it to keep the information instead of removing it. Therefore, what I mean is that when you do an update it will not remove the 2 but keep both the 2 and add the 1. If you’re interested I’ll send you the code.