Netlify Mailchimp subscribe Lambda function

mailchimp-subscribe.js

const Mailchimp = require('mailchimp-api-v3')
const validate = require('./validations')

const { MAILCHIMP_API_KEY } = process.env

exports.handler = async (event, context) => {
  // require an API key or throw everytime
  if (!MAILCHIMP_API_KEY) {
    return {
      statusCode: 500,
      body: 'process.env.MAILCHIMP_API_KEY must be defined',
    }
  }

  // badness if this throws
  const body = JSON.parse(event.body)

  // return forbidden if request requirements are invalid
  try {
    validate.is_email('body.email', body.email)
    // i think they're usually 10?
    validate.is_length('body.list_id', body.list_id, 4, 16)
  } catch (e) {
    return { statusCode: 403, body: e.message }
  }

  // prep request
  const API = new Mailchimp(MAILCHIMP_API_KEY)
  const path = `/lists/${body.list_id}/members`
  const request = create_request_body({
    email: body.email,
    interests: body.interests,
  })

  // make request
  let [statusCode, status, error] = [500, null, null]
  try {
    const result = await API.post({ path, body: request })
    statusCode = result.statusCode
    status = result.status
  } catch (e) {
    statusCode = e.status
    error = e.message
  }

  return {
    statusCode,
    body: JSON.stringify({
      subscribed: statusCode === 200,
      status,
      error,
    }),
  }
}

function create_request_body({
  email = '',
  interests = [],
  status = 'subscribed',
  merge_fields = {},
} = {}) {
  return {
    email_address: email,
    status,
    merge_fields,
    interests: interests.reduce((acc, cur) => ({ ...acc, [cur]: true }), {}),
  }
}

Example POST body:

{ "email": "yo@danny.dev", "list_id": "1234567890", "interests": ["asdf23414", "2342asdf"] }