Can't read property... InnerHTML of null

Question

How to solve this problem.....
https://code.sololearn.com/WEjNHokjaD5j/?ref=app

Answer 1

https://code.sololearn.com/WPAlki1G7rvZ/?ref=app

Answer 2

In your HTML you have "out" as a class instead of id. Change class="out" to id="out"