title: typescript extend base class object property
body: <p>First and foremost, I apologize, I'm completely new to OO programming and I'm sure there is a better way to word this question ( one that would probably yield a search result or 10 ). </p>
  
  <p>So to make my life easy and to explain what I want to do here's code</p>
  
  <pre><code>class A {
    propertyA = {
      itemA: "a",
      itemB: "b".
      itemC: "c"
    }
    propertyB = {
      itemA: "A"
    }
  }
  class B extends A {
    propertyA.itemD = "d";
    propertyB.itemB = "B";
  }
  </code></pre>
  
  <p>I get an error when I try to do this. I basically need the base class to be a template and extend a few things here and there with the extending class. Otherwise it only needs all the other properties ( I just don't want to retype them for each class )</p>