title: Event like componentDidUpdate, but fired only once
body: <p>I have some components that should do some work as soon as their data has arrived and rendered for the first time, but not for future rerenderings. For example: Comments are loaded and rendered, now 1. load social media libraries and 2. load some Google Analytics.</p>
  
  <p>Right now I'm doing it like that:</p>
  
  <pre><code>componentDidUpdate: function (prevProps, prevState) {
      if (this.hasAlreadyUpdatedOnce) {
          // ... do some stuff...
      } else {
          // ... do some stuff that should happen only once...
          // 1. load social media libraries
          // 2. load some Google Analytics
          this.hasAlreadyUpdatedOnce = true;
      }
  }
  </code></pre>
  
  <p>But I'm asking myself if there's a more elegant way than setting a property like that.</p>