Why is here error? (innerHTML)

Question

Cannot set property 'innerHTML' of null
How to fix this???
https://code.sololearn.com/WJqqDIl7dG7L/?ref=app

Answer 1

https://code.sololearn.com/W9n9L0Y6CyCz/?ref=app

Answer 2

Thank you!

Answer 3

as long as you pass the this keyword as argument to the add function you don't even need to do this:
// document.getElementById(cell).InnerHTML = "X";
you can just do something like that:
// cell.InnerHTML = "X";