Why is 'for(var item in list)' with arrays considered bad practice in JavaScript?

Question

Given a simple zero based, numerically indexed array:

var list = [\'Foo\', \'Bar\', \'Baz\'];

Many times, I have noticed that when someone

Answer 1

Speed?

for(..;..;..) loop proved to be 36 times faster than for .. in when I tested it here.

Link courtesy this SO answer