Possibly save 2 hours of your time: One day I open a .js file on my Visual Studio and it shows a blank or empty screen. No code is displayed.
Luckily I am able to use the repair feature and restart computer to get this working again.
Search on Windows start menu >> Programs and Features
Right click on Visual Studio 2015 and click Change.
Then click on Repair. This next part may take over an hour so it is probably best to do this at end of day.
Finally, after the repair is completed, it may show some errors. Please make sure to capture and copy those errors to another file for reference later if needed. It will ask you to restart your computer. Hopefully, you can now open the .js file successfully.