title: React intl return [object Object]
body: <p>I am trying to use react intl to translate the page of my site. <a href="https://github.com/yahoo/react-intl" rel="nofollow noreferrer">Github</a></p>
  
  <p>json lang :</p>
  
  <pre><code>fr.json : 
  {
      "errorPage.title": Erreur 404"
  }
  
  en.json : 
  {
      "errorPage.title": Error 404"
  }
  </code></pre>
  
  <p>I have that on my js file</p>
  
  <pre><code>const title = &lt;FormattedMessage id="errorPage.title" defaultMessage="Erreur 404" /&gt;
  
  document.title = title;
  </code></pre>
  
  <p>That return on my title page this [object Object]</p>
  
  <p>How i can do ?
  Thank's !</p>