Sync with upstream @ a0bfa924

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

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

@@ -12,8 +12,13 @@
 
 Σε αυτό το σημείο, να συμπληρώσω οτι η JavaScript έχει μεγάλη διάφορα με την [Java](https://en.wikipedia.org/wiki/Java_(programming_language)).
 
+<<<<<<< HEAD
 '''smart header="Γιατί <u>Java</u>Script?"
 Όταν είχε φτιαχτεί η JavaScript, είχε ένα διαφορετικό όνομά, λεγότανε "LiveScript". Αλά η Java ήταν πολύ γνωστή εκείνη την εποχή, οπότε αποφασίστηκε οτι θα βοηθούσε αν έκαναν την γλωσσά προγραμματισμού τον "μικρο αδελφό" της Java.
+=======
+```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.
+>>>>>>> a0bfa924a17cad8e7fee213904b27dbf57c2dbac
 
 Αλλά καθώς εξελίχθηκε, η JavaScript έγινε μια πλήρως ανεξάρτητη γλώσσα με τη δική της προδιαγραφή που ονομάζεται [ECMAScript] (http://en.wikipedia.org/wiki/ECMAScript), και τώρα δεν έχει καμία σχέση με την Java
 
@@ -90,7 +95,11 @@ JavaScript is the only browser technology that combines these three things.
 
 That's what makes JavaScript unique. That's why it's the most widespread tool for creating browser interfaces.
 
+<<<<<<< HEAD
 While planning to learn a new technology, it's beneficial to check its perspectives. So let's move on to the modern trends affecting it, including new languages and browser abilities.
+=======
+That said, JavaScript also allows to create servers, mobile applications, etc.
+>>>>>>> a0bfa924a17cad8e7fee213904b27dbf57c2dbac
 
 ## Languages "over" JavaScript
 

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

@@ -5,11 +5,11 @@ This book is a *tutorial*. It aims to help you gradually learn the language. But
 
 ## Specification
 
-**The ECMA-262 specification** contains the most in-depth, detailed and formalized information about JavaScript. It defines the language.
+[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.
 
-The latest draft is at <https://tc39.es/ecma262/>.
+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>.
 
@@ -24,7 +24,7 @@ Also, if you're in developing for the browser, then there are other specs covere
     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 referrerd to as JScript). If one needs something specific to Internet Explorer, better go there: <http://msdn.microsoft.com/>.
+- **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".
 

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

@@ -32,6 +32,7 @@ In practice, lightweight editors may have a lot of plugins including directory-l
 The following options deserve your attention:
 
 - [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.

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!
 
-This part of the tutorial is about core JavaScript, the language itself. 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"

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.

1-js/02-first-steps/04-variables/article.md

@@ -12,7 +12,7 @@ A [variable](https://en.wikipedia.org/wiki/Variable_(computer_science)) is a "na
 
 To create a variable in JavaScript, use the `let` keyword.
 
-The statement below creates (in other words: *declares* or *defines*) a variable with the name "message":
+The statement below creates (in other words: *declares*) a variable with the name "message":
 
 ```js
 let message;
@@ -237,7 +237,7 @@ To declare a constant (unchanging) variable, use `const` instead of `let`:
 const myBirthday = '18.04.1982';
 ```
 
-Variables declared using `const` are called "constants". They cannot be changed. An attempt to do so would cause an error:
+Variables declared using `const` are called "constants". They cannot be reassigned. An attempt to do so would cause an error:
 
 ```js run
 const myBirthday = '18.04.1982';
@@ -290,7 +290,7 @@ In other words, capital-named constants are only used as aliases for "hard-coded
 
 Talking about variables, there's one more extremely important thing.
 
-A variable name should have a clean, obvious meaning, describe the data that it stores.
+A variable name should have a clean, obvious meaning, describing the data that it stores.
 
 Variable naming is one of the most important and complex skills in programming. A quick glance at variable names can reveal which code was written by a beginner versus an experienced developer.
 
@@ -323,7 +323,7 @@ Modern JavaScript minifiers and browsers optimize code well enough, so it won't
 
 We can declare variables to store data by using the `var`, `let`, or `const` keywords.
 
-- `let` -- is a modern variable declaration. The code must be in strict mode to use `let` in Chrome (V8).
+- `let` -- is a modern variable declaration.
 - `var` -- is an old-school variable declaration. Normally we don't use it at all, but we'll cover subtle differences from `let` in the chapter <info:var>, just in case you need them.
 - `const` -- is like `let`, but the value of the variable can't be changed.
 

1-js/02-first-steps/05-types/article.md

@@ -178,7 +178,7 @@ The `object` type is special.
 
 All other types are called "primitive" because their values can contain only a single thing (be it a string or a number or whatever). In contrast, objects are used to store collections of data and more complex entities. We'll deal with them later in the chapter <info:object> after we learn more about primitives.
 
-The `symbol` type is used to create unique identifiers for objects. We have to mention it here for completeness, but it's better to study this type after objects.
+The `symbol` type is used to create unique identifiers for objects. We mention it here for completeness, but we'll study it after objects.
 
 ## The typeof operator [#type-typeof]
 

1-js/02-first-steps/06-type-conversions/1-primitive-conversions-questions/solution.md

@@ -14,11 +14,22 @@ true + false = 1
 " -9  " - 5 = -14 // (4)
 null + 1 = 1 // (5)
 undefined + 1 = NaN // (6)
+" \t \n" - 2 = -2 // (7)
 ```
 
+<<<<<<< HEAD
 1. Η πρόσθεση με μια συμβολοσειρά όπως π.χ. `"" + 1`, μετατρέπει το `1` σε μια συμβολοσειρά: `"" + 1 = "1"`, και τότε έχουμε `"1" + 0`, όπου ο ίδιος κανόνας εφαρμόζεται.
 2. Η αφαίρεση `-` (όπως στις περισσότερες Μαθηματικές πράξεις) λειτουργεί μόνο με αριθμούς, και μετατρέπει μια άδεια συμβολοσειρά `""` σε `0`.
 3. Η πρόσθεση με μια συμβολοσειρά, τοποθετεί τον αριθμό `5` στη συμβολοσειρά (επιπλέον παράδειγμα: `5 +"9" = "59"`).
 4. Η αφαίρεση μετατρέπει τις τιμές πάντα σε αριθμούς, επομένως εδώ μετατρέπει το `"  -9  "` στον αριθμό `-9` (αγνοώντας τα κενά γύρω του).
 5. Η `null` γίνεται `0` μετά την αριθμητική μετατροπή.
 6. Η `undefined` γίνεται `NaN` μετά την αριθμητική μετατροπή.
+=======
+1. The addition with a string `"" + 1` converts `1` to a string: `"" + 1 = "1"`, and then we have `"1" + 0`, the same rule is applied.
+2. The subtraction `-` (like most math operations) only works with numbers, it converts an empty string `""` to `0`.
+3. The addition with a string appends the number `5` to the string.
+4. The subtraction always converts to numbers, so it makes `"  -9  "` a number `-9` (ignoring spaces around it).
+5. `null` becomes `0` after the numeric conversion.
+6. `undefined` becomes `NaN` after the numeric conversion.
+7. Space characters, are trimmed off string start and end when a string is converted to a number. Here the whole string consists of space characters, such as `\t`, `\n` and a "regular" space between them. So, similarly to an empty string, it becomes `0`.
+>>>>>>> a0bfa924a17cad8e7fee213904b27dbf57c2dbac

1-js/02-first-steps/06-type-conversions/1-primitive-conversions-questions/task.md

@@ -21,6 +21,7 @@ true + false
 "  -9  " - 5
 null + 1
 undefined + 1
+" \t \n" - 2
 ```
 
 Σκεφτείτε καλά, γράψτε κάτω τις απαντήσεις σας και μετά συγκρίνετε τες με την απάντηση.

1-js/02-first-steps/06-type-conversions/article.md

@@ -10,7 +10,7 @@
 Σε αυτό το κεφάλαιο, δεν θα καλύψουμε την ύλη για τα αντικείμενα. Αντίθετα, θα μελετήσουμε πρώτα τις απλές τιμές. Αργότερα, όταν μάθουμε για τα αντικείμενα, θα δούμε πώς δουλεύει η μετατροπή των αντικειμένων στο κεφάλαιο <info:object-toprimitive>.
 ```
 
-## ToString
+## String Conversion
 
 Η μετατροπή συμβολοσειρών γίνεται όταν χρειαζόμαστε μια τιμή σε μορφή συμβολοσειράς.
 
@@ -30,7 +30,7 @@ alert(typeof value); // string
 
 Η μετατροπή συμβολοσειρών είναι αρκετά προφανής. Η `false` γίνεται `"false"`, η `null` γίνεται `"null"`, κλπ.
 
-## ToNumber
+## Numeric Conversion
 
 Η μετατροπή αριθμών γίνεται αυτόματα σε Μαθηματικές συναρτήσεις και εκφράσεις.
 
@@ -94,7 +94,7 @@ alert( '1' + 2 ); // '12' (συμβολοσειρά στα αριστερά)
 Αυτό συμβαίνει μόνο όταν τουλάχιστον μία από τις παραμέτρους είναι μια συμβολοσειρά. Διαφορετικά, οι τιμές μετατρέπονται σε αριθμούς.
 ````
 
-## ToBoolean
+## Boolean Conversion
 
 Η μετατροπή αληθοτιμών είναι η πιο απλή.
 
@@ -116,13 +116,23 @@ alert(Boolean("")); // false
 ```
 ````
 
+<<<<<<< HEAD
 ## Περίληψη
 
 Οι τρεις πιο διαδεδομένα χρησιμοποιούμενες μετατροπές τύπων, είναι: σε συμβολοσειρά, σε αριθμό, και σε αληθοτιμή.
 
 **`ToString`** -- Γίνεται όταν κάτι το δίνουμε ως έξοδο. Μπορεί να εφαρμοστεί με τη `String(value)`. Η μετατροπή σε συμβολοσειρά είναι συνήθως προφανής για τις απλές τιμές.
 
 **`ToNumber`** -- Γίνεται στις Μαθηματικές πράξεις. Μπορεί να εφαρμοστεί με τη `Number(value)`.
+=======
+## Summary
+
+The three most widely used type conversions are to string, to number, and to boolean.
+
+**`String Conversion`** -- Occurs when we output something. Can be performed with `String(value)`. The conversion to string is usually obvious for primitive values.
+
+**`Numeric Conversion`** -- Occurs in math operations. Can be performed with `Number(value)`.
+>>>>>>> a0bfa924a17cad8e7fee213904b27dbf57c2dbac
 
 Η μετατροπή ακολουθεί τους κανόνες:
 
@@ -133,7 +143,11 @@ alert(Boolean("")); // false
 |<code>true&nbsp;/&nbsp;false</code> | `1 / 0` |
 | `string` | Η συμβολοσειρά διαβάζεται "όπως είναι", τα κενά και από τις δύο πλευρές αγνοούνται. Μια άδεια συμβολοσειρά γίνεται `0`. Ένα σφάλμα δίνει `NaN`. |
 
+<<<<<<< HEAD
 **`ToBoolean`** -- Γίνεται σε λογικές πράξεις. Μπορεί να εφαρμοστεί με τη `Boolean(value)`.
+=======
+**`Boolean Conversion`** -- Occurs in logical operations. Can be performed with `Boolean(value)`.
+>>>>>>> a0bfa924a17cad8e7fee213904b27dbf57c2dbac
 
 Ακολουθεί τους κανόνες: