* Remove a given listener from this event target. * @param {string} eventName The event name to remove. * @param {Function} listener The listene

* @param callback return true for continue,false for break * @return boolean true: break visit;

* Check whether a given value is an object or not. * @param {any} x The value to check. * @returns {boolean} `true` if the value is an object.

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* preformance key(refChild == null)

* attributes; * children; * * writeable properties: * nodeValue,Attr:value,CharacterData:data * prefix