Is it js write in head or body tag ? What is the difference?

Answer 1

https://code.sololearn.com/WA7HLbc7nU4A/?ref=app

1.in head that will throw null because of <b> not fully loaded yet

while in body That is opposite

2.place your script inside body will be faster than place in head

Answer 2

You actually should realise what head and body are for.
Head is for writing information not displayed directly in the code such as
meta,link,script&style(also in body)
The ones you wanna see is in the body, such as
h1 h4 p progress table

Etc.