title: What does it mean to say, default keys in map?
body: <p><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Keyed_collections" rel="nofollow">Here</a>, it says, <em>An <code>Object</code> has a prototype, so there are default keys in the map. However, this can be bypassed using <code>map = Object.create(null)</code>.</em> </p>
  
  <p>I could not understanding the meaning of <code>map = Object.create(null)</code>. </p>
  
  <p>1) What does it mean to set <code>map.__proto__</code> to <code>null</code>?</p>
  
  <p>2) In the above paragraph, what does it mean to say, default keys of map?</p>
  
  <p>3) How these default keys are related to <code>Object</code> having a prototype?</p>