Wait Until OData Request Completed

I have a requirement to oData service inside onExit hook method. I have written below code but unfortunately oData service is not getting called as view is destroyed immediately . Is there any way to add wait or delay the destroy of view until oData read request is complete ?

window.addEventListener("beforeunload", (event) => { this.fnUnlockGremienVersion();

         var s;
            event = event || window.event;
            if (this._PreviousGreVersion) {
             s = "Your most recent changes are still being saved. " +
                    "If you close the window now, they may not be saved.";
                event.returnValue = s;
                return s;                    
            }
         
        });