title: Why do we need the isPrototypeOf at all?
body: <p><a href="https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/IsPrototypeOf">this page</a> states:</p>
  
  <blockquote>
    <p>Note: isPrototypeOf differs from
    instanceof operator. In the expression
    object instanceof AFunction, the
    object prototype chain is checked
    against AFunction.prototype, not
    against AFunction itself</p>
  </blockquote>
  
  <p>Ok I don't really get what they are trying to tell us. Isn't <code>object instanceof AFunction</code> exactly the same as `AFunction.prototype.isPrototypeOf(object)? or am I wrong?</p>
  
  <p>Why do we need the <code>isPrototypeOf</code> at all? </p>
  
  <p>If i ever need to do <code>p.isPrototypeOf(o)</code> couldn't I just do <code>o instanceof p.constructor</code> ?</p>
  
  <p>Addtionally, is <code>p.isPrototypeOf(o)</code> functionally equivalent to <code>p===Object.getPrototypeOf(o)</code>?</p>