Rule Definition
Every time the interpreter encounters a dot character, it will look up the child variable against the parent. For example, var hourHand=myGrandFather.clock.hands.hour make three lookup. When used too much in a loop, dot notation can affect performance of a javascript function. Reducing the dotation usage can win 50% of the time consumed by this function.

Remediation
Use intermediate variable to minimize the number of dot within the loop.

Violation Code Sample

for (var i=0;i<data;i+=1){ 
  var hourHand=myGrandFather.clock.hands.hour; 
  var minuteHand=myGrandFather.clock.hands.minute; 
  var secondHand=myGrandFather.clock.hands.second; 
  ... 
} // VIOLATION "myGrandFather.clock.hands" has been referenced more than 2 times

Fixed Code Sample

for (var i=0;i<data;i+=1){ 
  var hands = myGrandFather.clock.hands; 
  var hourHand=hands.hour; 
  var minuteHand=hands.minute; 
  var secondHand=hands.second; 
  ... 
}

AJAX in Action - Manning - ISBN 1-932394-61-3 page 296