Why you should wrap your (JavaScript) dependencies

An email sending example.

• Example using SendGrid
• How do we consume this?
• Switching to another email provider

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Example using SendGrid

On a very basic level, we want to be able to send emails.

In code terms, we want a send function. What’s nice to have is a way to abstract the message creation, that’s a makeMailMessage function.

See the following code:

const sgMail = require('@sendgrid/mail');

const {
  SENDGRID_API_KEY,
  EMAIL_OVERRIDE_TO_ADDRESS,
  EMAIL_FROM_ADDRESS
} = process.env;

sgMail.setApiKey(SENDGRID_API_KEY);

function makeMailMessage ({
  to,
  from = EMAIL_FROM_ADDRESS,
  subject,
  text,
  html
}) {
  return {
    to: EMAIL_OVERRIDE_TO_ADDRESS || to,
    from,
    subject,
    ...(html ? { html } : { text })
  };
}
function send (message) {
  return sgMail.send(message);
}
module.exports = {
  makeMailMessage,
  send
};

How do we consume this?

function doSomeSending(name, email) {
  const message = makeMailMessage({
    from: '[e-mail]',
    to: email,
    subject: 'Welcome to Code with Hugo',
    text: `Hi ${name}, welcome to Code with Hugo.`
  });
  return send(message); 
}

Switching to another email provider

Say we want to switch to another provider, namely Mailgun. Ideally, we don’t want to change any of the application code.

const {
  MAILGUN_API_KEY,
  EMAIL_DOMAIN,
  EMAIL_OVERRIDE_TO_ADDRESS,
  EMAIL_FROM_ADDRESS
} = process.env;
const mailgun = require('mailgun-js')({
  apiKey: MAILGUN_API_KEY,
  domain: EMAIL_DOMAIN
});

function makeMailMessage ({
  to,
  from = EMAIL_FROM_ADDRESS,
  subject,
  text,
  html
}) {
  return {
    to: EMAIL_OVERRIDE_TO_ADDRESS || to,
    from,
    subject,
    ...(html ? { html } : { text })
  };
}

function send (message) {
  return new Promise((resolve, reject) => {
    mailgun.messages().send(message, (error, body) => {
      if (error) {
        return reject(error);
      }
      resolve(body);
    });
  });
}

module.exports = {
  makeMailMessage,
  send
};

The API for our mail module stays the same, but we’ve changed the provider under the hood 👍 .

Samuel Zeller