JSメソッドの「eventCallBack」から値を返す方法
JS関数の定義を参照してください。
window.plugins.GCM.register("428641231987", "GCM_Event", this.GCM_Success, this.GCM_Fail);
ここ
@param senderId - GCM service identifier
@param eventCallback - {String} - Name of global window function that will handle incoming events from GCM
@param successCallback - {Function} - called on success on registering device
@param failureCallback - {Function} - called on failure on registering device
「GCM_Event」で生成された値を返したい
var requiredValue = window.plugins.GCM.register("428641231987", "GCM_Event", this.GCM_Success, this.GCM_Fail);
requiredValueに値が欲しい