Sync with upstream @ ec21af8a

.gitattributes

@@ -1 +1,2 @@
 * text=auto eol=lf
+*.svg       binary

1-js/01-getting-started/1-intro/article.md

@@ -6,14 +6,23 @@ Keling, JavaScript-da nima muhimligini, u bilan nimaga erisha olishimizni va qan
 
 *JavaScript* dastlab *"veb-sahifalarni jonlantirish"* uchun yaratilgan edi.
 
+<<<<<<< HEAD
 Ushbu tilda dasturlar *skript* deb nomlanadi. Ular veb-sahifani HTML-da yozilishi mumkin va sahifa brauzer tomonidan yuklanganidan keyin ular avtomatik ravishda amalga oshiriladi.
+=======
+The programs in this language are called *scripts*. They can be written right in a web page's HTML and run automatically as the page loads.
+>>>>>>> ec21af8aef6930388c06ee4cd8f8f6769f9d305b
 
 Skriptlar oddiy matn sifatida taqdim etiladi va amalga oshiriladi. Ularni ishga tushirish uchun maxsus tayyorgarlik yoki kompilatsiya kerak emas.
 
 Shu jihatdan, JavaScript [Java] (https://en.wikipedia.org/wiki/Java_(programming_language)) tilidan juda farq qiladi.
 
+<<<<<<< HEAD
 ```smart header="Nega <u>Java</u>Script?"
 JavaScript yaratilganda, u dastlab "LiveScript" nomi bilan taqdim etilgan edi. Ammo Java o'sha paytlarda juda mashhur edi, shuning uchun Java tilining "ukasi" sifatida yangi tilni taqdim etish g'oyasi JS mashhur bo'lishga yordam beradi deb hisoblangan .
+=======
+```smart header="Why is it called <u>Java</u>Script?"
+When JavaScript was created, it initially had another name: "LiveScript". But Java was very popular at that time, so it was decided that positioning a new language as a "younger brother" of Java would help.
+>>>>>>> ec21af8aef6930388c06ee4cd8f8f6769f9d305b
 
 Ammo, rivojlanish jarayonida, JavaScript [ECMAScript] (http://en.wikipedia.org/wiki/ECMAScript) deb ataladigan o'z xususiyatiga ega to'liq mustaqil tilga aylangan va hozirda Java tiliga hech qanday aloqasi yo'q.
 ```
@@ -70,7 +79,7 @@ Examples of such restrictions include:
     There are ways to interact with camera/microphone and other devices, but they require a user's explicit permission. So a JavaScript-enabled page may not sneakily enable a web-camera, observe the surroundings and send the information to the [NSA](https://en.wikipedia.org/wiki/National_Security_Agency).
 - Different tabs/windows generally do not know about each other. Sometimes they do, for example when one window uses JavaScript to open the other one. But even in this case, JavaScript from one page may not access the other if they come from different sites (from a different domain, protocol or port).
 
-    This is called the "Same Origin Policy". To work around that, *both pages* must contain a special JavaScript code that handles data exchange.
+    This is called the "Same Origin Policy". To work around that, *both pages* must agree for data exchange and contain a special JavaScript code that handles it. We'll cover that in the tutorial.
 
     This limitation is, again, for the user's safety. A page from `http://anysite.com` which a user has opened must not be able to access another browser tab with the URL `http://gmail.com` and steal information from there.
 - JavaScript can easily communicate over the net to the server where the current page came from. But its ability to receive data from other sites/domains is crippled. Though possible, it requires explicit agreement (expressed in HTTP headers) from the remote side. Once again, that's a safety limitation.
@@ -92,9 +101,13 @@ JavaScript - bu uchta narsani birlashtirgan yagona brauzer texnologiyasidir.
 
 Bu JavaScript-ni noyob qiladi. Shuning uchun u brauzer interfeyslarini yaratishda eng keng tarqalgan vositadir.
 
+<<<<<<< HEAD
 Yangi texnologiyani o'rganishni rejalashtirayotib, uning istiqbollarini tekshirish ham muhimdir. Keling, zamonaviy tendentsiyalarga o'taylik.
 
 ## JavaScript "ustidan" qo'llanadigan tillar
+=======
+That said, JavaScript also allows to create servers, mobile applications, etc.
+>>>>>>> ec21af8aef6930388c06ee4cd8f8f6769f9d305b
 
 JavaScript-ning sintaksisi hammaning ehtiyojlariga mos kelmaydi. Turli odamlar turli xususiyatlarni xohlashadi.
 
@@ -110,9 +123,18 @@ Bunday tillarning namunalari:
 - [TypeScript] (http://www.typescriptlang.org/) murakkab tizimlarni ishlab chiqish, soddalashtirish va qo'llab-quvvatlash uchun "strict data typing"ni qo'shishga qaratilgan. Microsoft tomonidan ishlab chiqilgan.
 - [Dart] (https://www.dartlang.org/) brauzer bo'lmagan muhitda (mobil ilovalar kabi) ishlaydigan o'z dvigateliga ega bo'lgan mustaqil til. Bu dastlab JavaScript uchun zaxira sifatida Google tomonidan taklif etildi, lekin hozirgi paytda, brauzerlar shu tilni ham JS-ga transpilatsiya bo'lishini talab qilishadi.
 
+<<<<<<< HEAD
 Bundan ham ko'proq tillar mavjud. Albatta, biz bu tillardan birini ishlatsak ham, biz nima qilayotganimizni tushunish uchun JavaScript-ni bilishimiz kerak.
 
 ## Xulosa
+=======
+- [CoffeeScript](http://coffeescript.org/) is a "syntactic sugar" for JavaScript. It introduces shorter syntax, allowing us to write clearer and more precise code. Usually, Ruby devs like it.
+- [TypeScript](http://www.typescriptlang.org/) is concentrated on adding "strict data typing" to simplify the development and support of complex systems. It is developed by Microsoft.
+- [Flow](http://flow.org/) also adds data typing, but in a different way. Developed by Facebook.
+- [Dart](https://www.dartlang.org/) is a standalone language that has its own engine that runs in non-browser environments (like mobile apps), but also can be transpiled to JavaScript. Developed by Google.
+
+There are more. Of course, even if we use one of transpiled languages, we should also know JavaScript to really understand what we're doing.
+>>>>>>> ec21af8aef6930388c06ee4cd8f8f6769f9d305b
 
 - JavaScript dastlab brauzer tili sifatida yaratilgan, ammo hozirgi paytda ko'pgina boshqa muhitlarda ham qo'llanilmoqda.
 - Bugun JavaScript HTML/CSS bilan to'la integratsiyalashgan va eng keng tarqalgan brauzer tili hisoblanadi.

1-js/01-getting-started/2-manuals-specifications/article.md

@@ -0,0 +1,42 @@
+
+# Manuals and specifications
+
+This book is a *tutorial*. It aims to help you gradually learn the language. But once you're familiar with the basics, you'll need other sources.
+
+## Specification
+
+[The ECMA-262 specification](https://www.ecma-international.org/publications/standards/Ecma-262.htm) contains the most in-depth, detailed and formalized information about JavaScript. It defines the language.
+
+But being that formalized, it's difficult to understand at first. So if you need the most trustworthy source of information about the language details, the specification is the right place. But it's not for everyday use.
+
+A new specification version is released every year. In-between these releases, the latest specification draft is at <https://tc39.es/ecma262/>.
+
+To read about new bleeding-edge features, including those that are "almost standard" (so-called "stage 3"), see proposals at <https://github.com/tc39/proposals>.
+
+Also, if you're in developing for the browser, then there are other specs covered in the [second part](info:browser-environment) of the tutorial.
+
+## Manuals
+
+- **MDN (Mozilla) JavaScript Reference** is a manual with examples and other information. It's great to get in-depth information about individual language functions, methods etc.
+
+    One can find it at <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference>.
+
+    Although, it's often best to use an internet search instead. Just use "MDN [term]" in the query, e.g. <https://google.com/search?q=MDN+parseInt> to search for `parseInt` function.
+
+
+- **MSDN** – Microsoft manual with a lot of information, including JavaScript (often referred to as JScript). If one needs something specific to Internet Explorer, better go there: <http://msdn.microsoft.com/>.
+
+    Also, we can use an internet search with phrases such as "RegExp MSDN" or "RegExp MSDN jscript".
+
+## Compatibility tables
+
+JavaScript is a developing language, new features get added regularly.
+
+To see their support among browser-based and other engines, see:
+
+- <http://caniuse.com> - per-feature tables of support, e.g. to see which engines support modern cryptography functions: <http://caniuse.com/#feat=cryptography>.
+- <https://kangax.github.io/compat-table> - a table with language features and engines that support those or don't support.
+
+All these resources are useful in real-life development, as they contain valuable information about language details, their support etc.
+
+Please remember them (or this page) for the cases when you need in-depth information about a particular feature.

1-js/01-getting-started/2-code-editors/article.md → 1-js/01-getting-started/3-code-editors/article.md

@@ -12,14 +12,12 @@ An IDE loads the project (which can be many files), allows navigation between fi
 
 If you haven't selected an IDE yet, consider the following options:
 
-- [WebStorm](http://www.jetbrains.com/webstorm/) for frontend development. The same company offers other editors for other languages (paid).
-- [Netbeans](http://netbeans.org/) (free).
+- [Visual Studio Code](https://code.visualstudio.com/) (cross-platform, free).
+- [WebStorm](http://www.jetbrains.com/webstorm/) (cross-platform, paid).
 
-All of these IDEs are cross-platform.
+For Windows, there's also "Visual Studio", not to be confused with "Visual Studio Code". "Visual Studio" is a paid and mighty Windows-only editor, well-suited for the .NET platform. It's also good at JavaScript. There's also a free version [Visual Studio Community](https://www.visualstudio.com/vs/community/).
 
-For Windows, there's also "Visual Studio", not to be confused with "Visual Studio Code." "Visual Studio" is a paid and mighty Windows-only editor, well-suited for the .NET platform. A free version of it is called [Visual Studio Community](https://www.visualstudio.com/vs/community/).
-
-Many IDEs are paid but have a trial period. Their cost is usually negligible compared to a qualified developer's salary, so just choose the best one for you.
+Many IDEs are paid, but have a trial period. Their cost is usually negligible compared to a qualified developer's salary, so just choose the best one for you.
 
 ## Lightweight editors
 
@@ -33,21 +31,12 @@ In practice, lightweight editors may have a lot of plugins including directory-l
 
 The following options deserve your attention:
 
-- [Visual Studio Code](https://code.visualstudio.com/) (cross-platform, free) also has many IDE-like features.
 - [Atom](https://atom.io/) (cross-platform, free).
+- [Visual Studio Code](https://code.visualstudio.com/) (cross-platform, free).
 - [Sublime Text](http://www.sublimetext.com) (cross-platform, shareware).
 - [Notepad++](https://notepad-plus-plus.org/) (Windows, free).
 - [Vim](http://www.vim.org/) and [Emacs](https://www.gnu.org/software/emacs/) are also cool if you know how to use them.
 
-## My favorites
-
-The personal preference of the author is to have both an IDE for projects and a lightweight editor for quick and easy file editing.
-
-I'm using:
-
-- As an IDE for JS -- [WebStorm](http://www.jetbrains.com/webstorm/) (I switch to one of the other JetBrains offerings when using other languages)
-- As a lightweight editor -- [Sublime Text](http://www.sublimetext.com) or [Atom](https://atom.io/).
-
 ## Let's not argue
 
 The editors in the lists above are those that either I or my friends whom I consider good developers have been using for a long time and are happy with.

1-js/01-getting-started/3-devtools/article.md → 1-js/01-getting-started/4-devtools/article.md

@@ -50,11 +50,11 @@ Open Preferences and go to the "Advanced" pane. There's a checkbox at the bottom
 
 Now `key:Cmd+Opt+C` can toggle the console. Also, note that the new top menu item named "Develop" has appeared. It has many commands and options.
 
-## Multi-line input
-
+```smart header="Multi-line input"
 Usually, when we put a line of code into the console, and then press `key:Enter`, it executes.
 
-To insert multiple lines, press `key:Shift+Enter`.
+To insert multiple lines, press `key:Shift+Enter`. This way one can enter long fragments of JavaScript code.
+```
 
 ## Summary
 

1-js/02-first-steps/01-hello-world/article.md

@@ -1,6 +1,6 @@
 # Hello, world!
 
-The tutorial that you're reading is about core JavaScript, which is platform-independent. Later on, you'll learn about Node.js and other platforms that use it.
+This part of the tutorial is about core JavaScript, the language itself.
 
 But we need a working environment to run our scripts and, since this book is online, the browser is a good choice. We'll keep the amount of browser-specific commands (like `alert`) to a minimum so that you don't spend time on them if you plan to concentrate on another environment (like Node.js). We'll focus on JavaScript in the browser in the [next part](/ui) of the tutorial.
 
@@ -46,7 +46,7 @@ The `<script>` tag contains JavaScript code which is automatically executed when
 The `<script>` tag has a few attributes that are rarely used nowadays but can still be found in old code:
 
 The `type` attribute: <code>&lt;script <u>type</u>=...&gt;</code>
-: The old HTML standard, HTML4, required a script to have a `type`. Usually it was `type="text/javascript"`. It's not required anymore. Also, the modern HTML standard, HTML5, totally changed the meaning of this attribute. Now, it can be used for JavaScript modules. But that's an advanced topic; we'll talk about modules in another part of the tutorial. 
+: The old HTML standard, HTML4, required a script to have a `type`. Usually it was `type="text/javascript"`. It's not required anymore. Also, the modern HTML standard totally changed the meaning of this attribute. Now, it can be used for JavaScript modules. But that's an advanced topic; we'll talk about modules in another part of the tutorial.
 
 The `language` attribute: <code>&lt;script <u>language</u>=...&gt;</code>
 : This attribute was meant to show the language of the script. This attribute no longer makes sense because JavaScript is the default language. There is no need to use it.
@@ -60,7 +60,7 @@ Comments before and after scripts.
     //--></script>
     ```
 
-    This trick isn't used in modern JavaScript. These comments hid JavaScript code from old browsers that didn't know how to process the `<script>` tag. Since browsers released in the last 15 years don't have this issue, this kind of comment can help you identify really old code.
+    This trick isn't used in modern JavaScript. These comments hide JavaScript code from old browsers that didn't know how to process the `<script>` tag. Since browsers released in the last 15 years don't have this issue, this kind of comment can help you identify really old code.
 
 
 ## External scripts
@@ -73,9 +73,7 @@ Script files are attached to HTML with the `src` attribute:
 <script src="/path/to/script.js"></script>
 ```
 
-Here, `/path/to/script.js` is an absolute path to the script file (from the site root).
-
-You can also provide a relative path from the current page. For instance, `src="script.js"` would mean a file `"script.js"` in the current folder.
+Here, `/path/to/script.js` is an absolute path to the script from the site root. One can also provide a relative path from the current page. For instance, `src="script.js"` would mean a file `"script.js"` in the current folder.
 
 We can give a full URL as well. For instance:
 

1-js/02-first-steps/03-strict-mode/article.md

@@ -4,7 +4,7 @@ For a long time, JavaScript evolved without compatibility issues. New features w
 
 That had the benefit of never breaking existing code. But the downside was that any mistake or an imperfect decision made by JavaScript's creators got stuck in the language forever.
 
-This was the case until 2009 when ECMAScript 5 (ES5) appeared. It added new features to the language and modified some of the existing ones. To keep the old code working, most modifications are off by default. You need to explicitly enable them with a special directive: `"use strict"`.
+This was the case until 2009 when ECMAScript 5 (ES5) appeared. It added new features to the language and modified some of the existing ones. To keep the old code working, most such modifications are off by default. You need to explicitly enable them with a special directive: `"use strict"`.
 
 ## "use strict"
 
@@ -19,9 +19,7 @@ For example:
 ...
 ```
 
-We will learn functions (a way to group commands) soon.
-
-Looking ahead, let's just note that `"use strict"` can be put at the start of most kinds of functions instead of the whole script. Doing that enables strict mode in that function only. But usually, people use it for the whole script.
+We will learn functions (a way to group commands) soon. Looking ahead, let's note that `"use strict"` can be put at the beginning of the function body instead of the whole script. Doing that enables strict mode in that function only. But usually, people use it for the whole script.
 
 
 ````warn header="Ensure that \"use strict\" is at the top"
@@ -53,9 +51,17 @@ For the future, when you use a browser console to test features, please note tha
 
 Sometimes, when `use strict` makes a difference, you'll get incorrect results.
 
-Even if we press `key:Shift+Enter` to input multiple lines, and put `use strict` on top, it doesn't work. That's because of how the console executes the code internally.
+You can try to press `key:Shift+Enter` to input multiple lines, and put `use strict` on top, like this:
+
+```js
+'use strict'; <Shift+Enter for a newline>
+//  ...your code
+<Enter to run>
+```
+
+It works in most browsers, namely Firefox and Chrome.
 
-The reliable way to ensure `use strict` would be to input the code into console like this:
+If it doesn't, the most reliable way to ensure `use strict` would be to input the code into console like this:
 
 ```js
 (function() {

1-js/02-first-steps/04-variables/2-declare-variables/solution.md

@@ -1,4 +1,4 @@
-First, the variable for the name of our planet.
+## The variable for our planet
 
 That's simple:
 
@@ -8,7 +8,7 @@ let ourPlanetName = "Earth";
 
 Note, we could use a shorter name `planet`, but it might be not obvious what planet it refers to. It's nice to be more verbose. At least until the variable isNotTooLong.
 
-Second, the name of the current visitor:
+## The name of the current visitor
 
 ```js
 let currentUserName = "John";

1-js/02-first-steps/04-variables/3-uppercast-constant/solution.md

@@ -2,4 +2,4 @@ We generally use upper case for constants that are "hard-coded". Or, in other wo
 
 In this code, `birthday` is exactly like that. So we could use the upper case for it.
 
-In contrast, `age` is evaluated in run-time. Today we have one age, a year after we'll have another one. It is constant in a sense that it does not change through the code execution. But it is a bit "less of a constant" than `birthday`, it is calculated, so we should keep the lower case for it.
+In contrast, `age` is evaluated in run-time. Today we have one age, a year after we'll have another one. It is constant in a sense that it does not change through the code execution. But it is a bit "less of a constant" than `birthday`: it is calculated, so we should keep the lower case for it.