MongoDB / Node.JS: Get attribute value from document

I have a document:

{
"_id":ObjectId("someID")
"email":"john@example.com"
}

I would like to retrieve "john@example.com" so that I can pass this value to the browser.

How do I do that?

I saw these SO posts, but I don't understand the solution at all:
How to get string value inside a Mongodb document?
How to get value from a MongoDB document