title: JavaScript - File is instance of File, but `instanceof File` is false
body: <p>I have an <code>&lt;input type="file"&gt;</code> with a local file selected, which I would like to upload to the server as a File, not as a Blob. I'm grabbing it with jQuery (element and then <code>.files[0]</code> or <code>.prop('files')[0]</code>).</p>
  
  <p>By every indication but one, the prototype of this object is File:</p>
  
  <pre><code>Object.getPrototypeOf(file) // =&gt; File {slice: function}
  file.__proto__              // =&gt; File {slice: function}
  file.constructor            // =&gt; function File() { [native code] }
  file.constructor.prototype  // =&gt; File {slice: function}
  </code></pre>
  
  <p>And yet:</p>
  
  <pre><code>file instanceof File        // =&gt; false
  file instanceof Blob        // =&gt; true
  </code></pre>
  
  <p>What gives? </p>