title: How to listen state changes in react.js?
body: <p>What is the angular's $<a href="https://docs.angularjs.org/api/ng/type/$rootScope.Scope#$watch">watch</a> function equivalent in React.js? </p>
  
  <p>I want to listen state changes and call a function like getSearchResults().</p>
  
  <pre><code>componentDidMount: function() {
      this.getSearchResults();
  }
  </code></pre>