Confused

Question

https://code.sololearn.com/WoOCdvsepc7G/?ref=app
I was coding simple incremental game,it's gives me error,I looked anything but seems I can't find it

Sorry I'm a beginner at website development

Answer 1

Put your javascript inside a window.onload function:
window.onload = () => {
// ...
};

Answer 2

Thanks for the solution