Overview

This is simple server-side ab-testing middleware for use on high traffic Node.JS sites. This middleware lets you create consistent tests that can run both on the backend and the frontend, allowing you to create complex tests across pages.

Requirements

• Node & Express
• express-session

Setup

First, install the package.

npm install easy-abtest

Then add the package to your app.js file:

const abtest = require('easy-abtest');

If you use static middleware, set up the module afterwards (otherwise it runs on every static call too).

app.use(abtest({
  enabled: true,
  name: 'experiment-ID-here',
  buckets: [
    {variant: 0, weight: 0.40},
    {variant: 1, weight: 0.60}
  ]
}));

In the buckets property, please use an array of variants, and the weights must add up to 1.

The name is your experiment slug. If you use Google Optimize, for example, this should be your Experiment ID.

Once added, the middleware makes available the following properties:

• In your routers: req.session.test
• In your views: abTest

Usage

In your routers

Decide what happens based on the bucket:

  let headline;
  if (req.session.test.bucket == 0) {
    headline = 'Struggling with homework?';
  } else if (req.session.test.bucket == 1) {
    headline = 'Our homework helper can help you now.';
  }

  ...
  return res.render('games', {
    headline: headline
  });

In your views:

  h1 #{headline}
  if abTest.bucket == 0
    button Click here now
  else if abTest.bucket == 1
    button Start today!

You can also tie the test to a reporting system, like Google Optimize & Analytics:

  script.
    let abTest = !{JSON.stringify(abTest)};
    gtagPayload['experiments'] = [ { id: abTest.name, variant: parseInt(abTest.bucket) } ];

  h1 #{headline}

  if abTest.bucket == 0
    button#cta Click here now
  else if abTest.bucket == 1
    button#cta Start today!

  script.
    $('#cta').on('click', function() {
      gtag('event', abTest.bucket, {
        'event_category': abTest.name,
        'event_label': 'start today'
      });
    });