let title = {};
let existingTitle = {......};
Object.assign(title, existingTitle);
title.id = newID //From where every that may be.
// Do other stuff with the title object.
// Then clear the title object after you've done everything.
title = {};
Be careful, this method has some problems creating a "deep" copy of the existing object. The only true way to get a deep copy is by doing title = JSON.parse(JSON.stringify(existingTitle)). So if the above method doesn't work then use the stringify method. But of course this comes at a price of execution in javascript.