Auth0 rule for sending emails of signed up users to Mailchimp.

mailchimp.js

/*
*  Update a Mailchimp list with user emails during the signup or the first login.
*
*  Create the following atributes in the Auth0 RULE configuration settings.
*  https://auth0.com/docs/rules/guides/configuration
* 
*  MC_TOKEN: Mailchimp API Token. E.g.: ef235a44355dda3e61ea074ae0d439a2-us20
*  MC_LIST_ID: ID of the Mailchimp list you would like to populate. E.g.: ca9eb2555e
*  MC_API_URL: Mailchimp API URL. E.g.: https://us20.api.mailchimp.com/3.0
*
**/
function (user, context, callback) {

    // Short-circuit if the user signed up already
    if (context.stats.loginsCount > 1 || context.protocol === 'oauth2-refresh-token') {
        return callback(null, user, context);
      }
  
    const request = require('request');
  
    const ctx = {
        email_address: user.email,
        merge_fields : {"FNAME": user.given_name || "",
                        "LNAME": user.family_name || ""},
        status: "subscribed"
    };
 
    var auth = "Basic " + new Buffer("token:" + configuration.MC_TOKEN).toString("base64");

    request.post({
      url: configuration.MC_API_URL + "/lists/" + configuration.MC_LIST_ID + "/members",
      headers : {"Authorization" : auth},
      json: ctx
    });
  
    // Don’t wait for the Mailchimp call to finish, return right away (the request will continue on the sandbox)`
    callback(null, user, context);
}