title: How to declare a property with a dependency of other property in state constructor of React?
body: <p>I'm trying to create a class with some properties the second depends on the value of the first, but I want to initialize them.
  So this want I'm trying I just include ... in this example to simulate my component call.</p>
  
  <pre><code>constructor(props){
  super(props);
  this.state={
    Section:sectionsData.filter(function(section){return section.id=="id"}),
    questions : this.state.Section[0].questions.map(...)
  }
  </code></pre>
  
  <p>I'm getting "Cannot read property 'Section' of undefined"</p>
  
  <p>I've already tried to use the section value just as a member of the class like this </p>
  
  <pre><code>this.Section[0] 
  </code></pre>
  
  <p>But also did not work.</p>
  
  <p>And how can I update the value of those properties using  this.setState()</p>