Today I was sending a Mail to one of my friends and I was attaching a compressed file, I was pretty sure that it will get attached easily and then I will mail it to my friend, but during attachment, I start getting an error like "There were errors attaching your file(s)" and in compose mail window I saw an error message "Blocked for security reasons", At first I thought that my zipped folder might be containing some files whose extensions are violating Gmail policies, I thought the extensions might be .exe, or .jar or .msi cause I was aware of all these extensions that Gmail doesn't allow us to send these type of files via mail and block them for security reasons.
But there were no such files in my zipped folder, then I search on the Internet and got the news that Gmail has started blocking .js files as well and as a result now, we can not really attach it to our Mail.
From now on, If you want to share a .js file you will have to use Google Drive or other cloud services or some other mail clients. Using Gmail you won't be able to send a .js file.
It is surely been a commendable step from the most popular mail client that is Gmail to ensure more security for its users and I am happy to see such updates in Gmail cause we all use it as the primary source of sending and receiving emails.