Hi!

Please use npm run demo to execute the script. Output will be at data/output.json. I've also committed my result for your convenience.

There're some notes concerning my understanding of the assignment and its implementation:

• given that users' names are formatted as single string ("John Doe"), script will assume last word in the string is Last Name and first word is First Name (if present). Everything in between (like a middle name in "John Bartholomew Doe") is ignored, as it's not often included in emails.
• spec didn't specify how close the match of names should be, though it stated that [email protected] should match Michael Scott. So I've decided to let a user set an option of "how much shortened" names could be - default values are 2 first chars for First Name and 3 first chars for Last Name. You can play with it passing number arguments through CLI like that npm run demo 2 10 and see how many emails are recognized, if you'd like to.
• neither spec specified what should happen if no emails were matched for a given User. I've chosen to include {"user_email":"[email protected]", "related_emails":[] } in the output anyway, as probably the mailer (or whatever code will be using this data) will handle empty array just fine, while missing primary email could lead to a bug (like not sending any email to that user at all).
• I've assumed sample_data.json comes from some third-source so script can make sure only valid emails are added to its output. It can be turned off programmatically or by passing --no-validate flag in the demo's CLI.

Have a nice day!