Import Cost is a chrome extension which will show you the size of the JS file that you are accessing in browser.
Previously I had to download the file to find the size but with Import Cost extension it will show the file size instantly while viewing in a nice manner.
It will show you the size in following manner, if the size of the file is in
bytes => green background
KB => blue background
MB => red background
In addition to the styles this extension allows the user to move size element anywhere in the screen.