Take your skillset way beyond syntax expertise
What sets senior level JavaScript developers apart isn’t the breadth of their syntax knowledge. It’s the depth of their overall skillset.
Being a senior level JavaScript developer is not about memorising countless methods and properties, it’s about gaining a fundamental understanding of the way JavaScript “thinks”.
Here’s the rub: there isn’t always time in a project to dig into the how and why — not when there’s work to do and tickets to close. Gaining that understanding through trial and error, copied-and-pasted snippets, or working with frameworks that make tasks quicker and easier by papering over the gritty details can take a person years.
This course isn’t a catalogue of every method and property JavaScript has to offer; you won’t find any flash cards or vocab quizzes here. What we will cover are practical patterns that you can put to use in your work right away — regardless of your organisation’s preference in framework. We’re going to focus on the syntaxes you’re most likely to encounter in your day-to-day work, the ones that make up more advanced features of the language, and most importantly, the ones that will help you gain a better understanding of JavaScript, the language, as it is played.
My goal isn’t for you to walk away from this course knowing the whole of JavaScript — that’s impossible. My goal is to help you understand JavaScript: why it works the way it does, why sometimes things that feel like they should work don’t, and why things that feel like they shouldn’t work sometimes do. If you should find yourself hitting a wall, don’t stress: I’ll be here to help right alongside your peers in the JavaScript for Everyone Discord community.
Besides, JavaScript is big, and nearly as old as the web itself — no one should expect to absorb all of it all at once. This course is designed for you to take it as far as you’re comfortable, and the day you’re ready to learn about static initialisation blocks, or well-known Symbols, or the essential nature of this
, this course will be waiting here for you like an old friend.
If I wanted to learn something, I’d first check to see if Mat Marquis wrote about it. I know few people as skilled at breaking down complex ideas into human-sized chunks; I know even fewer folks who write with such easy, approachable wit.
I’ve learned so much from Mat over my career, and I’m excited I’ll be learning something new from him real soon. I can’t wait to check out JavaScript for Everyone.
I’d read Mat’s writing purely for pleasure. I’ve read a lot of technical writing in my time. It’s a skill to deliver technical correctness with clarity and brevity. Even then, rarely do you end up with anything fun. Mat reads like a grizzled poet, with more curly brackets than em dashes, teaching you just what you need right when you need it. It’s perfect, and you’ll end up wanting more.
Mat’s domain experience, moral compass, and playful rhetoric make him one of my favourite tech writers working today. Whatever he chooses to publish, you can rest assured that reading will broaden your horizons and lighten your spirits.
It might feel like a lofty goal — especially if you’re relatively new to the industry — but this course is designed to push everyone beyond where they thought they could be.
During this course, your overall skillset will be developed way beyond where it is now, even if you already hold a senior position. We’ll cover so much ground at a pace that works for you, you won't recognise yourself — for the better — when you complete JavaScript for Everyone. The hope is that you can then push your career beyond a level you ever thought possible.
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I remember way back when I first read one of Mat’s articles about responsive images. I’ve taken time to read everything he’s written since then, and every time it has been a delight. He has a gift for making the complicated, approachable and the dry, fun. He has a pragmatic sensibility that conveys the intricacies of a topic while still keeping the vibe of “but let’s play video games after this.”
If there’s a topic I don’t understand and Mat has written about it, I know that not only will I understand it after reading what he’s written, I’ll have a great time with it, too. Everything he writes goes to 11. Treat yourself.
Mat’s writing stands out in an industry that is full of unnecessary over-complication for complication’s sake. He takes technical concepts and breaks them down in a way that is direct, easy to understand, and oftentimes entertaining. JavaScript for Everyone is a gift for anyone looking to improve their understanding of the language that powers the web.
A lot of folks in tech spend their careers building enormous (and enormously intimidating) walls of complexity. Mat’s made his career out of smashing those walls: breaking ’em down with clarity and concision and making sure everything he puts into the world is inclusive, approachable, and, frankly – fun

Let’s clear up any worries you might have with some quick-fire answers.
When is the course going to be ready for purchase?
The Piccalilli team and I are aiming to launch this course in the early Autumn 2025, with an opportunity for you to get a large discount by pre-ordering the course in the summer.
What skills do I need to have?
To get the most from this course, you should have at least fundamental JavaScript skills. You can get those for free in my web.dev Learn JavaScript course. Anything above that, you’re more than qualified!
What other courses/books have you written?
I’m the author of JavaScript for Web Designers and Image Performance from A Book Apart. I also wrote the Learn JavaScript and Learn Images courses for Google’s web.dev.
Is there a set timeframe to complete the course?
The course is in a mixed-media, mostly written format with no timeframe. You can start whenever you like and pick it up when you have time available. There’s no set cohorts or timelines to work to.
How long does the course take?
Our advice is that the course should take around 12-20 hours to complete. Because this is a mostly written course, and people’s reading speeds are different, your mileage might vary, however.
What’s the refund policy?
I’m confident that you’re going to get a lot of value from this course, but if you are not happy with your purchase within 14 days, reach out to
[email protected]
and we’ll refund your purchase in full.
My name is Mat “Wilto” Marquis, and I build websites. I’m an independent designer, front-end developer, and consultant.
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What you get:
Support and community
Everyone who purchases JavaScript for Everyone gets access to an exclusive Discord community where you can get support from your instructor and your peers.
Comprehensive, structured learning
The course is delivered in an accessible, mixed media format that’s easy to consume and easy to pick up where you left off.
Lifetime access
Pay once and get lifetime access to all the current and future course material.
A certificate of completion
It’s really important for some organisations that you get a certificate of completion. We’ve got your back with that.
Customer support
Our customer support team —
[email protected]
— are ready to help out with queries whenever you have them.Effective use of training budgets
You’ll learn transferable and high quality, applicable skills, making this a sound investment of yours or your employer’s training budgets.
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