title: what is the difference between getDefaultProps and getInitialState react js
body: <p>I am new in react js.</p>
  
  <pre><code>getDefaultProps () {
      return {
          backgroundColor: 'gray',
          height: 200,
          width: 200
      }
  },
  </code></pre>
  
  <p>I've same values for <code>getDefaultProps</code> and for <code>getInitialState</code> :</p>
  
  <pre><code>getInitialState () {
      return {
          backgroundColor: 'gray',
          height: 200,
          width: 200
      }
  },
  </code></pre>
  
  <p>What is the logical difference in between both. which should supposed to override or which one will execute first. </p>
  
  <p>Thanks.</p>