title: What's the meaning of "=>" (an arrow formed from equals & greater than) in JavaScript?
body: <p>I know that the <code>&gt;=</code> operator means more than or equal to, but I've seen <code>=&gt;</code> in some source code. What's the meaning of that operator?</p>
  
  <p>Here's the code:</p>
  
  <pre class="lang-js prettyprint-override"><code>promiseTargetFile(fpParams, aSkipPrompt, relatedURI).then(aDialogAccepted =&gt; {
      if (!aDialogAccepted)
          return;
  
      saveAsType = fpParams.saveAsType;
      file = fpParams.file;
  
      continueSave();
  }).then(null, Components.utils.reportError);
  </code></pre>