Do you have access to a computer with a modern web browser and a text editor?
Do you prefer stimulating dinner party conversation to dry, dull, academic lectures?
this book is for you.
If you can answer “yes” to any one of these:
Are you completely new to web development?
Are you a kick-butt web developer looking for a reference book?
this book is not for you.
“How can this be a serious book?”
“What’s with all the graphics?”
“Can I actually learn it this way?”
Your brain craves novelty. It’s always searching, scanning, waiting for something unusual. It was built that way, and it helps you stay alive.
Today, you’re less likely to be a tiger snack. But your brain’s still looking. You just never know.
So what does your brain do with all the routine, ordinary, normal things you encounter? Everything it can to stop them from interfering with the brain’s real job—recording things that matter. It doesn’t bother saving the boring things; they never make it past the “this is obviously not important” filter.
How does your brain know what’s important? Suppose you’re out for a day hike and a tiger jumps in front of you. What happens inside your head and body?
Neurons fire. Emotions crank up. Chemicals surge.
And that’s how your brain knows...
This must be important! Don’t forget it!
But imagine you’re at home, or in a library. It’s a safe, warm, tiger-free zone. You’re studying. Getting ready for an exam. Or trying to learn some tough technical topic your boss thinks will take a week, ten days at the most.
Just one problem. Your brain’s trying to do you a big favor. It’s trying to make sure that this obviously non-important content doesn’t clutter up scarce resources. Resources that are better spent storing the really big things. Like tigers. Like the danger of fire. Like how you should never again snowboard in shorts.
And there’s no simple way to tell your brain, “Hey brain, thank you very much, but no matter how dull this book is, and how little I’m registering on the emotional Richter scale right now, I really do want you to keep this stuff around.”
Most of us did not take courses on metacognition or learning theory when we were growing up. We were expected to learn, but rarely taught how to learn.
The trick is to get your brain to see the new material you’re learning as Really Important. Crucial to your well-being. As important as a tiger. Otherwise, you’re in for a constant battle, with your brain doing its best to keep the new content from sticking.
There’s the slow, tedious way, or the faster, more effective way. The slow way is about sheer repetition. You obviously know that you are able to learn and remember even the dullest of topics, if you keep pounding on the same thing. With enough repetition, your brain says, “This doesn’t feel important to him, but he keeps looking at the same thing over and over and over, so I suppose it must be.”
The faster way is to do anything that increases brain activity, especially different types of brain activity. The things on the previous page are a big part of the solution, and they’re all things that have been proven to help your brain work in your favor. For example, studies show that putting words within the pictures they describe (as opposed to somewhere else in the page, like a caption or in the body text) causes your brain to try to make sense of how the words and picture relate, and this causes more neurons to fire. More neurons firing = more chances for your brain to get that this is something worth paying attention to, and possibly recording.
A conversational style helps because people tend to pay more attention when they perceive that they’re in a conversation, since they’re expected to follow along and hold up their end. The amazing thing is, your brain doesn’t necessarily care that the “conversation” is between you and a book! On the other hand, if the writing style is formal and dry, your brain perceives it the same way you experience being lectured to while sitting in a roomful of passive attendees. No need to stay awake.
But pictures and conversational style are just the beginning.
We used pictures, because your brain is tuned for visuals, not text. As far as your brain’s concerned, a picture really is worth 1024 words. And when text and pictures work together, we embedded the text in the pictures because your brain works more effectively when the text is within the thing the text refers to, as opposed to in a caption or buried in the text somewhere.
We used redundancy, saying the same thing in different ways and with different media types, and multiple senses, to increase the chance that the content gets coded into more than one area of your brain.
We used concepts and pictures in unexpected ways because your brain is tuned for novelty, and we used pictures and ideas with at least some emotional content, because your brain is tuned to pay attention to the biochemistry of emotions. That which causes you to feel something is more likely to be remembered, even if that feeling is nothing more than a little humor, surprise or interest.
We used a personalized, conversational style, because your brain is tuned to pay more attention when it believes you’re in a conversation than if it thinks you’re passively listening to a presentation. Your brain does this even when you’re reading.
We included more than 100 activities, because your brain is tuned to learn and remember more when you do things than when you read about things. And we made the exercises challenging-yet-do-able, because that’s what most people prefer.
We used multiple learning styles, because you might prefer step-by-step procedures, while someone else wants to understand the big picture first, while someone else just wants to see a code example. But regardless of your own learning preference, everyone benefits from seeing the same content represented in multiple ways.
We include content for both sides of your brain, because the more of your brain you engage, the more likely you are to learn and remember, and the longer you can stay focused. Since working one side of the brain often means giving the other side a chance to rest, you can be more productive at learning for a longer period of time.
And we included stories and exercises that present more than one point of view, because your brain is tuned to learn more deeply when it’s forced to make evaluations and judgements.
We included challenges, with exercises, and by asking questions that don’t always have a straight answer, because your brain is tuned to learn and remember when it has to work at something. Think about it—you can’t get your body in shape just by watching people at the gym. But we did our best to make sure that when you’re working hard, it’s on the right things. That you’re not spending one extra dendrite processing a hard-to-understand example, or parsing difficult, jargon-laden or overly terse text.
We used people. In stories, examples, pictures, etc., because, well, you’re a person. And your brain pays more attention to people than it does to things.
Slow down. The more you understand, the less you have to memorize.
Don’t just read. Stop and think. When the book asks you a question, don’t just skip to the answer. Imagine that someone really is asking the question. The more deeply you force your brain to think, the better chance you have of learning and remembering.
Do the exercises. Write your own notes.
We put them in, but if we did them for you, that would be like having someone else do your workouts for you. And don’t just look at the exercises. Use a pencil. There’s plenty of evidence that physical activity while learning can increase the learning.
Read the “There are No Dumb Questions”
That means all of them. They’re not optional sidebars—they’re part of the core content! Don’t skip them.
Make this the last thing you read before bed. Or at least the last challenging thing. Part of the learning (especially the transfer to long-term memory) happens after you put the book down. Your brain needs time on its own, to do more processing. If you put in something new during that processing-time, some of what you just learned will be lost.
Drink water. Lots of it.
Your brain works best in a nice bath of fluid. Dehydration (which can happen before you ever feel thirsty) decreases cognitive function.
Talk about it. Out loud.
Speaking activates a different part of the brain. If you’re trying to understand something, or increase your chance of remembering it later, say it out loud. Better still, try to explain it out loud to someone else. You’ll learn more quickly, and you might uncover ideas you hadn’t known were there when you were reading about it.
Listen to your brain.
Pay attention to whether your brain is getting overloaded. If you find yourself starting to skim the surface or forget what you just read, it’s time for a break. Once you go past a certain point, you won’t learn faster by trying to shove more in, and you might even hurt the process.
Your brain needs to know that this matters. Get involved with the stories. Make up your own captions for the photos. Groaning over a bad joke is still better than feeling nothing at all.
You’ve got to create a lot of new brain connections to learn to program. Sleep often; it helps.
This is a learning experience, not a reference book. We deliberately stripped out everything that might get in the way of learning whatever it is we’re working on at that point in the book. And the first time through, you need to begin at the beginning, because the book makes assumptions about what you’ve already seen and learned.
In this book, we teach you to use the great parts to best advantage, and we’ll point out the bad parts, and advise you to drive around them.
We don’t exhaustively cover every single aspect of the language.
This book advocates well-structured and readable code based on best practices.
You want to write code that you and other people can read and understand, code that will still work in next year’s browsers. You want to write code in the most straight-forward way so you can get the job done and get on to better things. In this book we’re going to teach you to write clear, well-organized code that anticipates change from the get-go. Code you can be proud of, code you’ll want to frame and put on the wall (just take it down before you bring your date over).
We encourage you to use more than one browser with this book.
Programming is serious business. You’re going to have to work, sometimes hard.
If you’ve already had some programming experience, then you know what we’re talking about. If you’re coming straight from Head First HTML and CSS, then you’re going to find writing code is a little, well, different. Programming requires a different way of thinking. Programming is logical, at times very abstract, and requires you to think in an algorithmic way. But no worries; we’re going to do all that in a brain-friendly way. Just take it a bit at a time, make sure you’re well nourished and get plenty of sleep. That way, these new programming concepts will really sink in.
The activities are NOT optional.
The exercises and activities in this book are not add-ons; they’re part of the core content of the book. Some of them are to help with memory, some are for understanding, and some will help you apply what you’ve learned. Don’t skip the exercises. The crossword puzzles are the only things you don’t have to do, but they’re good for giving your brain a chance to think about the words in a different context.
The redundancy is intentional and important.
One distinct difference in a Head First book is that we want you to really get it. And we want you to finish the book remembering what you’ve learned. Most reference books don’t have retention and recall as a goal, but this book is about learning, so you’ll see some of the same concepts come up more than once.
The examples are as lean as possible.
Our readers tell us that it’s frustrating to wade through 200 lines of an example looking for the two lines they need to understand. Most examples in this book are shown within the smallest possible context, so that the part you’re trying to learn is clear and simple. Don’t expect all of the examples to be robust, or even complete—they are written specifically for learning, and aren’t always fully-functional.
We’ve placed all the example files on the Web so you can download them. You’ll find them at
The ‘Brain Power’ exercises don’t usually have answers.
For some of them, there is no right answer, and for others, part of the learning experience of the Brain Power activities is for you to decide if and when your answers are right. In some of the Brain Power exercises you will find hints to point you in the right direction.
Get the code examples, help and discussion
You’ll find everything you need for this book online at
http://wickedlysmart.com/hfjs, including code sample files and additional support material including videos.
Thank you to our amazing review team
The amazing technical reviewers pictured above provided feedback above and beyond, and each made significant contributions to this book. The following reviewers also made contributions across different aspects of the book: Galina N. Orlova, J. Patrick Kelley, Claus-Peter Kahl, Rob Cleary, Rebeca Dunn-Krahn, Olaf Schoenrich, Jim Cupec, Matthew M. Hanrahan, Russell Alleen-Willems, Christine J. Wilson, Louis-Philippe Breton, Timo Glaser, Charmaine Gray, Lee Beckham, Michael Murphy, Dave Young, Don Smallidge, Alan Rusyak, Eric R. Liscinsky, Brent Fazekas, Sue Starr, Eric (Orange Pants) Johnson, Jesse Palmer, Manabu Kawakami, Alan McIvor, Alex Kelley, Yvonne Bichsel Truhon, Austin Throop, Tim Williams, J. Albert Bowden II, Rod Shelton, Nancy DeHaven Hall, Sue McGee, Francisco Debs, Miriam Berkland, Christine H Grecco, Elhadji Barry, Athanasios Valsamakis, Peter Casey, Dustin Wollam and Robb Kerley.
We’re also extremely grateful to our esteemed technical reviewer David Powers. The truth is we don’t write books without David anymore, he’s just saved our butts too many times. It’s getting a little like Elton and Bernie; we’re starting to ask ourselves if we actually could write a book without him. David helps us forces us to make the book more sound and technically accurate, and his second career as a standup comic really comes in handy when we’re tuning the more humorous parts of the book. Thank you once again David—you’re the ultimate professional and we sleep better at night knowing we’ve passed your technical muster.
A huge, massive thanks to our editor, Meghan Blanchette, who cleared the path for this book, removed every obstacle to its completion, waited patiently and sacrificed family time to get it done. She’s also the person who keeps us sane in our relationship with O’Reilly (and keeps O’Reilly sane in their relationship with us). We love you and can’t wait to collaborate with you again!
And another big shoutout to our Chief Editor Emeritus, Mike Hendrickson, who spearheaded this book from the very beginning. Thanks again Mike; none of our books would have happened without you. You’ve been our champion for well over a decade and we love you for it!
Also At O’Reilly:
Our sincerest thanks as well to the whole O’Reilly team: Melanie Yarbrough, Bob Pfahler and Dan Fauxsmith, who wrangled the book into shape; to Ed Stephenson, Huguette Barriere, and Leslie Crandell who led the way on marketing and we appreciate their out-of-the-box approach. Thanks to Ellie Volkhausen, Randy Comer and Karen Montgomery for their inspired cover design that continues to serve us well. Thank you, as always, to Rachel Monaghan for her hardcore copyedit (and for keeping it all fun), and to Bert Bates for his valuable feedback.
 The large number of acknowledgments is because we’re testing the theory that everyone mentioned in a book acknowledgment will buy at least one copy, probably more, what with relatives and everything. If you’d like to be in the acknowledgment of our next book, and you have a large family, write to us.