title: How do I declare a class with expandable properties in an angular application?
body: <p>How do I declare a class with expandable properties in an angular application? I want to be able to add new property or remove it any time I need. I don't want to add or remove it directly in developing area. Is this possible?</p>
  
  <p>let me explain what I want. There is a collection named as "Books" and initially has some fields like Book_Name, Author, Pages, price, date_of_publish. I intended to have a form in my application that allows me to define new field such as "category" to "Books" collection. Also I have a model called "Books" in my Angular application that it's properties comes from "Books" collection fields.
  Is there any way to add new property to my model according to my collection newly added field?</p>