Write wordpress plugin to save user localstorage in database

I store some user setting in browser localstorage. I need a javascript code where I can choose what data I want to save in database. Maybe in usermeta table? I also want to featch this data from database and use it in a page. I need a js function which I can call and then localstorage data will be save to database asynchronisly. Example: I have data like this: [login to view URL]("lastname", "Smith"); [login to view URL]("kay1", "value1"); I want to be able to send this data do user database asynchronously. And I want to get this data in a wordpress theme - so then I can use it with some javascritp.