why erorr

Question

I'm learning the object and when I try it why is there any erorr who can help me?
https://code.sololearn.com/W3qJFeYLu5Al/?ref=app

Answer 1

sololearn requires window.onload

https://code.sololearn.com/WVs08J9nVC6a/?ref=app

Answer 2

onload tells it to wait until the window is finished loading completely. You don't want your code to execute before the elements it is trying to reference are rendered. So you put it in an onload listener. It is an event handler like onclick.

Answer 3

brains
what is the use of onload please explain to me