When an event is being processed, you may want to know the state of the [shift] key on the keyboard.
This Boolean property returns true when the [shift] key is pressed and false when it is not.
This property reflects the state of the [shift] key at the instant when the event was triggered. The user may have released the key in the meantime, so you should not assume that if the [shift] key was pressed earlier on that it is still pressed when the event handler is being executed.
DOM level 2 event handling moves this property to the MouseEvent object.