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 CustomEvent.initCustomEvent() method initializes a CustomEvent object. If the event has already been dispatched, this method does nothing.
Events initialized in this way must have been created with the Document.createEvent() method. This method must be called to set the event before it is dispatched using EventTarget.dispatchEvent(). Once dispatched, it doesn't do anything anymore.
Note: Do not use this method anymore, as it is deprecated.
Rather than using the feature, instead use specific event constructors, like CustomEvent(). The page on Creating and triggering events gives more information about the way to use those.