The industrial revolution was built with steel, and the Internet revolution has been built with JavaScript. Forged and strengthened through constant iteration over the past 25 years, JavaScript's dominance in application development is now hard to question, but that wasn't always the case.

It took only ten days for Brendan Eich to make the first version of JavaScript. It felt fragile, but as history would have it, first impressions aren't everything. Today, every aspect of JavaScript—every detail you'll learn in this book—is the product of hours of debate. Not every decision is ideal and no programming language is perfect, but if you judge one by its ubiquity alone, JavaScript perhaps comes close. It is the only language you can deploy everywhere: servers, desktop browsers, mobile web browsers, and even native mobile applications.

JavaScript is now used by software engineers of all experience levels and backgrounds. It's used by those who care about well-designed, elegant software as well as those who simply want to hack things together to achieve business goals.

How you'll use it is entirely up to you. That power is yours.

Over my last 15 years of developing software, JavaScript tools and best practices have changed dramatically. My experience with the language began in 2004—back when Geocities, Yahoo Groups, and Macromedia Flash player dominated the scene. JavaScript felt like a toy, and I played with some of the popular sandboxes at the time: RSS and MySpace Profile Pages. Helping others modify and customize their personal sites felt like the Wild West and got me hooked.

When I started my first company, configuring a host for your database took days and JavaScript was embedded into your HTML. There were no frontend “applications”—it was all mostly just piecemeal functions. As Ajax became more popular, spearheaded by jQuery, a new world unfolded and applications grew far more robust. That movement accelerated to a breakneck speed and then, suddenly, powerful frameworks were released. Front-end models! Data binding! Route management! Reactive views! It was during this front-end revolution that I moved to Silicon Valley to help start a company founded by Lady Gaga, and quickly, millions of users began using my code. Having now been in Silicon Valley for quite some time, I've led open-source contributions, mentored more software engineers than I can count, and hit a bit of luck, too. My last company was acquired by Stripe in 2018, where I now work to build economic infrastructure for the Internet.

I had the pleasure of meeting Matt the day he first flew out to Palo Alto to lead engineering at a small startup. It was called Claco, and I had recently joined on as an advisor. His energy and passion for great software was apparent, and the fledgling company quickly produced a beautiful product. As has been the Silicon Valley standard since the days of HP, this startup was founded out of a house. But this was no normal home. It was a “hacker house,” where ten or so brilliant software engineers lived at any given moment. Although this was not high-class living—discarded bunk beds and chairs found on the street were commonplace—the quantity and quality of code written there, on a daily basis, was staggering. After work hours, most would simply shift their focus and instead build their side projects for another couple of hours. Those who didn't know how to code were frequently inspired, would get the itch to learn, and become capable within just weeks.

Matt was a driving force at the center of this productivity. He was the most experienced software engineer in the house, and also happened to be the cleanest and most professional, too. Having a formal degree in computer engineering wasn't the norm, so when you saw algorithms, performance calculations, and code written on the windows or whiteboard, you knew Matt was building his next big project. As I got to know him, we became close friends. His intellect, fondness for mentorship, and ability to turn most anything into an A- joke were all qualities I admired.

Even though Matt is an incredibly talented software engineer and engineering leader, it is truly his unique set of experiences and knowledge that make him one of the most qualified people in the world to write this book.

He hasn't just spent his time teaching others—he's done the work.

At Claco, he built out multiple entire products, end-to-end, to help teachers provide a better learning experience in their classrooms. At DoorDash, where he was the first engineer, he built out a robust logistics and delivery network that achieved hyper-growth and is now worth upwards of twelve billion dollars. Finally, at Google, Matt's software has been used by billions of people across the planet.

Massive ownership, massive growth, and massive scale. Most software engineers can go their entire career and experience only one of these, if they're lucky. Matt has not only done all three but has also become a best-selling author in his “spare time,” having written two other books on JavaScript and Angular. Honestly, I just hope his next book unveils the time machine schematics he's clearly hiding from us.

This book is a robust tool filled to the brim with JavaScript knowledge and real-world perspectives. I'm excited for you to continue learning and build whatever you can dream up. Pick it apart, take notes, and don't forget to open up that code editor—after all, the internet revolution is still in the early days!

—Zach Tratar

Software engineer at Stripe

Former co-founder and CEO of Jobstart