Can JavaScript be written in notepad in pc and save as . html initial?

Answer 1

I am not sure what your intention with that is but just in case you want to know how javascript code can be placed directly in the html document, have a look at the example here:
https://www.w3schools.com/Tags/tag_script.asp

Answer 2

Yes it is possible

Saving is in .html or htm represents we are creating a script