If you run the command npm start  and get the following error:
 SyntaxError: /demo-encryption-js/config.json: Unexpected end of JSON input    

full error code can look like this:

Problem: it means that your config.json  is empty. 

Solution: check your config.json  and fill it with your Virgil application credentials.  Check out this article to be sure that use right parameters for config.json file.

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