I went through the contact-manager tutorial and everything was working just fine.
When I tried to run it again after a week it shows a blank page and this error in my console:
Unhandled rejection ReferenceError: api is not defined
I have not changed any files in the project, so I have no idea why this happend.
I have to mention that several other projects that I have started has also been crashing when I tried to run them the day after(without making any changes at all).