This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
This feature has been removed from the Web standards. Though some browsers may still support it, it is in the process of being dropped. 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.
Event.returnValue property indicates if 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.
Event.preventDefault() instead of this non-standard method.
event.returnValue = bool; var bool = event.returnValue;
Although it was included in an old Working Draft of W3C DOM Level 2, this property is not part of any specification.