https://debugmode.net/2017/03/17/javascript-interview-day-2-can-you-explain-undefined-and-null/
origin - http://www.pipiscrew.com/?p=7226 can-you-explain-undefined-and-null
https://debugmode.net/2017/03/17/javascript-interview-day-2-can-you-explain-undefined-and-null/
origin - http://www.pipiscrew.com/?p=7226 can-you-explain-undefined-and-null