Sort JavaScript object by key

I need to sort JavaScript objects by key.

Hence the following:

{ 'b' : 'asdsad', 'c' : 'masdas', 'a' : 'dsfdsfsdf' }

Would become:

{ 'a' : 'dsfdsfsdf', 'b' : 'asdsad', 'c' : 'masdas' }