title: Why this has a value of undefined in the scope tab of google chrome dev tools? I was expecting this: window
body: <p>My script below uses <strong>reduce()</strong> method in order to transform the array <code>[[0, 1],[2, 3],[4, 5]]</code> into <code>[1, 2, 3, 4, 5]</code></p>
  
  <p>When debugging this script, I noticed that in the scope tab within Chrome dev tools(see screenshot below), <strong>this</strong> has a value of undefined. Could you explain to me why? I was expecting this: window.</p>
  
  <p>P.S: I know that there is <strong>flate()</strong> method but my question is about <strong>this</strong> value.</p>
  
  <p>Thank you in advance.</p>
  
  <pre><code>const flattened = [
    [0, 1],
    [2, 3],
    [4, 5]
  ].reduce(
    (acc, item) =&gt; {
      debugger;
      return acc.concat(item)
    }, []);
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/qMxNF.png" alt="Screenshot"></p>