How to fix 'TypeError: Error #1009' error in ActionScript3.0 Adobe Animate - actionscript-3

Question

I'm setting up a button on the first frame which when clicked will transfer the user to the 2nd frame using this code:
stop();
Btn_1.addEventListener(MouseEvent.CLICK, fl_ClickToGoToAndPlayFromFrame_2);
function fl_ClickToGoToAndPlayFromFrame_2(event:MouseEvent):void
{
gotoAndPlay(2);
}
and on the second frame, I set up a dynamic text that will perform a countdown using this code:
var myTimer:Timer = new Timer(1000,60); // every second for 60 seconds
myTimer.addEventListener(TimerEvent.TIMER, onTimer);
myTimer.addEventListener(TimerEvent.TIMER_COMPLETE, onComplete);
myTimer.start();
function onTimer(e: TimerEvent):void {
countdown_text.text = String(myTimer.repeatCount - myTimer.currentCount);
}
function onComplete(e: TimerEvent):void{
gotoAndStop(3);
}
the thing is keep getting TypeError: Error #1009 message after debugging it. I know the fault is in line 7 of the 2nd code but I have no idea what is wrong with it. Pls help!

Answer 1

I should see your source fla, but it is most likely related to countdown_text not being accessible in that frame. Error description is "Cannot access a property or method of a null object reference", that means it cannot find the reference which is "countdown_text".
It is very very bad practice to write AS directly in frames. Convert code into a class and assign it as a document class.
You can find Adobe documentation for document class here: https://helpx.adobe.com/animate/using/actionscript-publish-settings.html