How to confirm email address using express/node?

What you’re looking for is called “account verification” or “email verification”. There are plenty of Node modules that can perform this, but the principle goes like this:

• Your User model should have an active attribute that is false by default
• When the user submits a valid signup form, create a new User (who’s active will be false initially)
• Create a long random string (128 characters is usually good) with a crypto library and store it in your database with a reference to the User ID
• Send an email to the supplied email address with the hash as part of a link pointing back to a route on your server
• When a user clicks the link and hits your route, check for the hash passed in the URL
• If the hash exists in the database, get the related user and set their active property to true
• Delete the hash from the database, it is no longer needed

Your user is now verified.