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Correct intro chapter
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‎00_intro.txt‎

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:next_link: 01_values
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:load_files: ["js/code/00_intro.js"]
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= Introduction =
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This book is about talking to computers. Computers have become one of
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the fundamental tools of our time. Being able to communicate well with
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your tools is a useful skill. With the right mindset, it can also be a
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very entertaining activity.
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your tools is a useful skill. And with the right mindset, it can also
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be a very entertaining activity.
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There is something of an inherent gap between us, squishy biological
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organisms with a talent for social and spatial reasoning, and the
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outside of the machine.
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Graphical interfaces tend to be easier to figure out than
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language-based ones—spotting a button is quicker than learning a word.
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For this reason, they have become the dominant way to interact with
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consumer-oriented systems. Compare today's phones, where you can
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accomplish all kinds of tasks by tapping and swiping the elements that
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appear on the screen, with the ((Commodore 64)) of 1982, the device
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that introduced me to computing, where all you get is a blinking
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cursor, and you're supposed to take it from there by typing commands.
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language-based ones—spotting a button is quicker than learning a
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grammar. For this reason, they have become the dominant way to
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interact with consumer-oriented systems. Compare today's phones, where
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you can accomplish all kinds of tasks by tapping and swiping the
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elements that appear on the screen, with the ((Commodore 64)) of 1982,
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the device that introduced me to computing, where all you get is a
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blinking cursor, and you're supposed to take it from there by typing
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commands.
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Obviously, the touchscreen phone is more accessible, and it is
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entirely appropriate that such devices use a graphical interface. But
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compose the functionality provided by the system in new ways, and even
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to create your own building blocks.
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(((programming language)))
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With the Commodore 64, almost every task in the system was
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accomplished by giving commands in the machine's built-in language (a
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((BASIC)) dialect). This allowed users to gradually progress from
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simply using the computer (loading in programs) to actually
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programming it themselves. You were _in_ a programming environment
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from the start, rather than having to actively look for one.
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(((programming language))) With the Commodore 64, almost every task in
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the system was accomplished by giving commands in the machine's
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built-in language (a dialect of the ((BASIC)) programming language).
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This allowed users to gradually progress from simply using the
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computer (loading programs) to actually programming it themselves.
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You were _in_ a programming environment from the start, rather than
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having to actively look for one.
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indexsee:[web browser,browser]
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(((JavaScript,availability of)))(((browser))) This has been mostly
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lost with the shift towards graphical user interfaces. But the
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language-based interfaces, in the form of programming languages, are
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still there, on every machine, largely hidden from the casual user.
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One such language, JavaScript, is available on just about every
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consumer device nowadays, as part of a web browser.
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consumer device as part of a web browser.
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This book intends to show you how to use this language to instruct a
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computer to perform tasks for you.
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makes the computer do what it does, it is data in the computer's
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memory, yet it controls the actions performed on this same memory.
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Analogies that try to compare programs to objects we are familiar with
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tend to fall short. A superficially fitting one is that of a machine,
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since lots of separate parts tend to be involved, and to make the
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tend to fall short. A superficially fitting one is that of a
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machine—lots of separate parts tend to be involved, and to make the
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whole thing tick we have to consider the ways in which these parts
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interconnect and contribute to the operation of the whole.
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only a small set of well-understood techniques in their programs. They
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have composed strict rules (_“best practices”_) prescribing the form
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programs should have, and the more zealous among them will consider
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those go outside of these rules to be _bad_ programmers.
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those that go outside of this little safe zone to be _bad_
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programmers.
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What hostility to the richness of programming—to try to reduce it to
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something straightforward and predictable, to place a taboo on all the
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(((memory)))Each line of the program contains a single instruction. It
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could be written in English like this:
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[source,text/plain]
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----
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1. Store the number 0 in memory location 0.
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2. Store the number 1 in memory location 1.
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3. Store the value of memory location 1 in memory location 2.
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4. Subtract the number 11 from the value in memory location 2.
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5. If the value in memory location 2 is the number 0, continue with instruction 9.
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6. Add the value of memory location 1 to memory location 0.
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3. Store the value of memory location 1 in memory
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location 2.
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4. Subtract the number 11 from the value in memory
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location 2.
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5. If the value in memory location 2 is the number 0,
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continue with instruction 9.
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6. Add the value of memory location 1 to memory
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location 0.
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7. Add the number 1 to the value of memory location 1.
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8. Continue with instruction 3.
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9. Output the value of memory location 0.
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----
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(((naming)))(((variable)))Although that is already more readable than
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the soup of bits, it is still rather unpleasant. It might help to use
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(((ECMAScript)))After its adoption outside of Netscape, a standard
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document was written to describe the way the language should work, in
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an effort to make sure the various piece of software that claimed to
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an effort to make sure the various pieces of software that claimed to
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support JavaScript were actually talking about the same language. This
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is called the ECMAScript standard, after the organization that did the
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standardization. In practice, the terms ECMAScript and JavaScript can
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impossible in more rigid languages, and, as we will see in later
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chapters, it can be used to overcome some of JavaScript's
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shortcomings. After learning it properly and working with it for a
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while, I have really learned to _like_ this language.
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while, I have learned to really _like_ this language.
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(((JavaScript,versions of)))There have been several _versions_ of
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JavaScript. ECMAScript version 3 was the dominant, widely supported
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version in the time of JavaScript's ascent to dominance, roughly
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between 2000 and 2010. During this time, work was underway on an
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ambitious version 4, which planned a number of radical improvements
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and extensions to the langauge. Changing a living, widely used
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and extensions to the language. Changing a living, widely used
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language in such a radical way turned out to be politically difficult,
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and work on the 4th edition was abandoned in 2008, leading to the much
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less ambitious 5th edition coming out in 2009. We're now just reaching
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which JavaScript is used. Some databases, such as MongoDB and CouchDB,
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use JavaScript as their scripting and query language. Several
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platforms for desktop and server programming, most notably the
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_((node.js))_ project, the subject of chapter (NODE), are providing a
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_((node.js))_ project, the subject of chapter (FIXME), are providing a
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powerful environment for programming JavaScript outside of the
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browser.
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endif::tex_target[]
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Running JavaScript programs outside of this book's sandbox is also far
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from hard. You can opt to install node.js, and read enough of its
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Running JavaScript programs outside of this book's sandbox is also
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possible. You can opt to install node.js, and read enough of its
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documentation (or of chapter (NODE)) to figure out how to use it to
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run text files that contain programs. Or you can use your browser's
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developer console (typically found somewhere under a “tools” or
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“developer” menu) and play around in there. In chapter (WEB), the way
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in which JavaScript programs are embedded in web pages (HTML files) is
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explained. In the meantime, you could head over to `http://jsbin.com`
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for another friendly interface for running JavaScript code in a
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browser.
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evaluate text files that contain programs. Or you can use your
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browser's developer console (typically found somewhere under a “tools”
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or “developer” menu) and play around in there. In chapter (WEB), the
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way in which JavaScript programs are embedded in web pages (HTML
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files) is explained. In the meantime, you could head over to
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`http://jsbin.com` for another friendly interface for running
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JavaScript code in a browser.
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== Typographic conventions ==
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[source,javascript]
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-----
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function fac(n) {
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return n == 0 ? 1 : n * fac(n - 1);
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if (n == 0)
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return 1;
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else
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return fac(n - 1) * n;
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}
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Sometimes, in order to demonstrate what happens when certain
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expressions are evaluated, the produced value is written below, with
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two slashes and an arrow in front of it:
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Sometimes, in order to show the output that a program produces, the
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expected output is written below it, with two slashes and an arrow in
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front:
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[source,javascript]
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-----
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1 + 1
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// → 2
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console.log(fac(8));
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// → 40320
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-----
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Good luck!
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‎code/00_intro.js‎

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function range(start, end) {
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var out = [];
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for (var i = start; i <= end; i++) out.push(i);
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return out;
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}
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function sum(array) {
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return array.reduce(function(a, b) { return a + b; }, 0);
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}
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function fac(n) {
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if (n == 0)
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return 1;
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else
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return fac(n - 1) * n;
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}

‎html/ejs.css‎

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position: absolute;
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width: 2em;
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text-align: right;
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left: -2.5em; bottom: 0;
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left: -2.5em; top: 1px;
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font-size: 90%;
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}
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margin: 0 0 0 2em;
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padding: 0;
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position: relative;
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font-size: 95%;
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}
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blockquote p {
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color: #333;
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font-size: 95%;
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}
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blockquote:before {

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