A/B testing with JavaScript

Learn to run A/B tests for any client, on any website in any tool!


Are you waiting for developers?

There is a big demand for marketers that can come up with revenue-increasing A/B tests these days. At the same time, there is a big demand for developers. 

Here is the problem. Companies prioritize their developers on the most critical processes.

A/B testing is important, but you can’t run optimized websites when they are offline. This means that your A/B test requests get postponed or rejected because of a lack of resources.

How will you be able to keep your clients happy if you can’t come up with results?

I worked as an A/B tester for years and this was my biggest frustration. I had so many awesome ideas but no one was running my A/B tests.

This needed to change so I decided to run A/B tests by myself. I started using the visual editors that come with most A/B testing tools. Although this helped me to get started, it quickly became a limit. I wanted to do more than simple changes and avoid the risk of breaking the website.

I needed to learn to code my own A/B tests to break that barrier. So that’s what I did. I spend three years coding and running my own A/B tests while getting lots of wins in the process.

By learning to write code I did not have to wait for developers anymore. I felt free!

Do you want to be able to take on any client?


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“I must say your content is awesome. Just wanted to say thanks so much.” – Ana Catarina Cizilio

⭐⭐⭐⭐⭐

“Your course gives a fresh perspective of doing A/B tests, something that is a very big part of CRO.” – Pramathesh

⭐⭐⭐⭐⭐

“Keep up the good work!” – Luka Nikolić

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“Finally, someone who codes something more complex than changing a title.” –  Panagiotis Stamoulis

⭐⭐⭐⭐⭐

“Not just simple JS commands! The lessons included all information I wanted to see, about actions, elements, and functions. I would only allow exercises to be more flexible!” – Dionysia

⭐⭐⭐⭐⭐

Awesome course, you’ll learn all the basics to get started with using JavaScript for your experiments. Looking forward to the new chapters that will be added!– Sander Volbeda


Chapter 0: Preparation

Set up a workspace to code A/B tests for every testing tool!

Chapter 1: Selecting

Start with selecting the elements on any website you want.

Chapter 2: Action

Make the changes you need to A/B test any hypothesis!

Chapter 3: Condition

Avoid test pollution by activating A/B tests with your rules!

Chapter 4: Targeting

Prevent websites from breaking by controlling where your experiment runs.

Chapter 5: Flickering

Prevent your users from seeing both variants of your A/B test by running lightning-fast code!


€ 197,-

JavaScript for Optimizers

  • Do you want to run A/B tests for any client?
  • Want to celebrate all your wins with your clients?
  • Ready to break free from your developers?

With these easy-to-change scripts for marketers, you will be able to run A/B tests on any website! Every script contains a video guide showing you how to use it!


Get more clients by showing your skills!

Don’t worry about convincing your clients to work with you. By removing the need for developers you made yourself an extremely valuable asset. When you complete the course you will receive the certificate that proves you are beyond visual editors that break websites.


Frequently asked questions

How is the course structured?

The course contains 94 video lessons supported by working code examples and 11 quizzes!

How long does it take to finish the course?

My first students completed the course in about 8 hours. It really depends on your ability to grasp these concepts. Just take your time and you will learn the most. You don’t need to finish the entire course before applying it. Some students use the examples as a library while they are creating A/B tests.

What A/B testing tools can you use?

JavaScript works in every testing tool. The course includes tutorials for these platforms:



What if I don’t like the course?

You get your money back! Contact me within 30 days of your purchase and I will give you a full refund.

When does the course start and finish?

The course starts when you enroll and finishes when you click “complete” on all the lessons and exercises.

When do I get my certificate?

You will get your certificate when you finish all the lessons and exercises.

How long do I have access to the course?

You will get lifetime access to all course material and future updates.

Is the course updated?

Yes, and you will get access to all the new updates for free!

What requirements do I need before starting the course?

No prior coding experience is needed to complete this course. If you know how A/B testing works you should be good to go.

Does the price of the course include taxes?

No, the price you see on this page is without taxes, therefore, the final price might increase on the checkout page based on your billing address.

Have more questions

Send me an e-mail at info@jeroenwiersma.com with all your questions!


A sample lesson from the course

In this lesson from chapter 2, you will learn to select your first element with JavaScript.


Buy the course to learn A/B testing for any client!