as of my previous question what is the difference between document.write() and console.log()

Answer 1

document.write method output to the DOM while console.log output to the browser console, which is hidden to the user by default.

You can learn more by searching at MDN site. 😉

Answer 2

good luck altering Facebook's source code

Answer 3

document.write( ) is a function that litturally puts text inside of your body, this should only really be used when you don't have a page, as you can't really control what document.write does.
console.log( ) is a cleaner method which will log only in the console, on normal browsers this is only shown when developer tools is opened

Answer 4

the passwords like fb, gmail are shown i dots to user. if we can alter the page source code of printing password from console.log() to document.write() then can we see the password i.e by user