title: Javascript: dictionary/object membership check speed
body: <p>I was curious as of what would be the fastest way to check if a JS object (used as a dictionary) has a given property.</p>
  
  <p>And I was baffled by the results. See for yourself: <a href="http://jsperf.com/object-membership-check-speed/6" rel="nofollow">http://jsperf.com/object-membership-check-speed/6</a></p>
  
  <p>In Chrome, the <code>in</code> keyword method is 96% slower than the dot syntax.
  And in Firefox, it's also around 80% slower. IE shows about 50% slower</p>
  
  <p>What the hell? Am I doing something wrong?
  I imagined the "in" keyword would be optimized, since it doesn't even need to get the value, it just returns a boolean. But apparently I was plain wrong.</p>