Catholic catalog by mailThe observation accepts a type-safe Key and an onChange callback. It eagerly begins listening to the UserDefaults value changes, specified by the key.; The observeValue() method is called by the KVO system automatically, when the value, specified by the key, is changed.The method accepts a change dictionary, from where we extract the old and new values and pass them to the onChange callback.Series 70 1911 manufacturersThey can choose either a single value or multiple values at a time. In the above example, (using input box), we have used two different methods to capture the changes in an element. We can apply similar procedures to get the changed or selected values, that is, either using $('#element') as selector or the $('#id') as a selector.