Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.
The Event property returnValue indicates whether the default action for this event has been prevented or not.
It is set to true by default, allowing the default action to occur. Setting this property to false prevents the default action.
Note: While returnValue has been adopted into the DOM standard, it is present primarily to support existing code. Use preventDefault(), and defaultPrevented instead of this historical property.