Netlify function to tag subscribers in ConvertKit

tag.js

// Netlify function to tag subscribers in ConvertKit
// https://www.netlify.com/products/functions/
// POST to /.netlify/functions/tag?id={subscriberId} with JSON array of tag ids: `[{tagId}, {tagId}, ...]`

const request = require("request-promise");

const apiKey = process.env.CONVERTKIT_API_KEY;
const apiSecret = process.env.CONVERTKIT_API_SECRET;

exports.handler = function(event, context, callback) {
  let headers = {};
  if (process.env.NODE_ENV === "dev") {
    headers["Access-Control-Allow-Origin"] = "*"
  }

  if (event.httpMethod !== "POST") {
    return callback(null, {
      statusCode: 200, // Return 200 for CORS/OPTIONS
      headers: headers,
      body: "please send a post request",
    });
  }

  const tagIds = JSON.parse(event.body);
  const params = event.queryStringParameters || {};
  const subscriberId = params.id;
  const subscriberUrl = `https://api.convertkit.com/v3/subscribers/${subscriberId}?api_secret=${apiSecret}`;

  // Get the subscriber record
  request.get({
    uri: subscriberUrl,
    json: true,
    simple: false,
    resolveWithFullResponse: true,
  }).then((res) => {
    if (res.statusCode !== 200) {
      return callback(null, {
        statusCode: 422,
        headers: headers,
        body: `error: invalid get response: ${res.statusCode}`,
      });
    }

    // Subscribe them to the tag
    const email = res.body.subscriber.email_address
    Promise.all(
      tagIds.map(function(tagId) {
        return request.post({
          url: `https://api.convertkit.com/v3/tags/${tagId}/subscribe?api_key=${apiKey}&email=${encodeURIComponent(email)}`
        });
      })
    ).then(() => {
      callback(null, {
        statusCode: 200,
        headers: headers,
        body: "ok",
      });
    }).catch(callback);
  }).catch(callback);
}