What am I doing wrong?

Question

I'm trying to replace all of the T`s with "Test". Why won't it work?
https://code.sololearn.com/W58SKmyWLd2Y/?ref=app

Answer 1

https://code.sololearn.com/WZeXsqtzp13b/?ref=app

Answer 2

Try replacing str.value with str.innerHTML.