Answer 1

Js can run at back end, it's node.js framework. console.log() usually outputs in javascript console of what's in its parenthesis, used for testing purpose of an application. While documentation.write() outputs on DOM. let keyword is used to declare variable in es6 because to not let the same variable declared again. While in var keyword you can re declare the same variable again and again which can cause some bugs as the application gets larger.

Answer 2

Yathin Babu
Just letting you know there's a typo in your answer 'nose.js' => 'node.js'

Answer 3

Oops auto correct by my keyboard 😅 thank you for letting me know.