if (propertyNames.length != previousState.length
            && previousState.length != currentState.length)

(1 != 2) && (2 != 3) -> true  ok
(1 != 1) && (1 != 2) -> false !!! WRONG should be true
(1 != 2) && (2 != 2) -> false !!! WRONG should be true
(1 != 1) && (1 != 1) -> false ok


should be

if (propertyNames.length != previousState.length
            || previousState.length != currentState.length)

(1 != 2) || (2 != 3) -> true  ok
(1 != 1) || (1 != 2) -> true ok
(1 != 2) || (2 != 2) -> true ok
(1 != 1) || (1 != 1) -> false ok