Merge pull request #20 from javascript-tutorial/sync-97ef8624

Sync with upstream @ 97ef862

Author: szcsl

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

@@ -111,7 +111,11 @@ Néhány példa:
 - [Flow](http://flow.org/): szintén a szigorúbb típusosságot valósítja meg, de a TypeScripttől eltérő módon. A Facebook fejlesztése.
 - [Dart](https://www.dartlang.org/): önálló nyelv, saját, böngészőn kívüli motorral. JavaScriptté alakítható. A Google fejlesztése.
 - [Brython](https://brython.info/) is a Python transpiler to JavaScript that enables the writing of applications in pure Python without JavaScript.
+<<<<<<< HEAD
 - [Kotlin](https://kotlinlang.org/docs/js-overview.html): egy modern, tömör, biztonságos programozási nyelv, amellyel böngésző és Node alá is fejleszthetünk .
+=======
+- [Kotlin](https://kotlinlang.org/docs/reference/js-overview.html) is a modern, concise and safe programming language that can target the browser or Node.
+>>>>>>> 97ef86242f9f236b13152e1baf52a55c4db8728a
 
 A fentieken túl számos más JavaScripten alapuló nyelv létezik. Még akkor is, ha egy JavaScriptté alakítandó nyelvvel dolgozunk, mindenképpen érdemes alaposan ismerni a JavaScriptet, hogy valóban értsük, hogyan működik a programunk.
 

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

@@ -13,20 +13,32 @@ Minden évben új ECMAScript verzió jelenik meg. A soronkövetkező verzió akt
 
 A legújabb nyelvi lehetőségekről és a szabványossá válás előtt álló, úgynevezett 3-as szintű előterjesztésekről a <https://github.com/tc39/proposals> oldalon tájékozódhatunk.
 
+<<<<<<< HEAD
 Böngészoldali programok írásához további specifikációkkal ismerkedhetünk meg a [második részben](info:browser-environment).
+=======
+Also, if you're in developing for the browser, then there are other specifications covered in the [second part](info:browser-environment) of the tutorial.
+>>>>>>> 97ef86242f9f236b13152e1baf52a55c4db8728a
 
 ## Leírások
 
+<<<<<<< HEAD
 - A **Mozilla Developer Network (MDN) JavaScript Referencia** egy mélyreható, széleskörű, példákkal illusztrált leírás a nyelv működéséről, a nyelvi elemekről, a beépített függvényekről és a böngészőben elérhető egyéb technológiákról.
+=======
+- **MDN (Mozilla) JavaScript Reference** is the main manual with examples and other information. It's great to get in-depth information about individual language functions, methods etc.
+>>>>>>> 97ef86242f9f236b13152e1baf52a55c4db8728a
 
     A referencia a <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference> oldalon található.
 
+<<<<<<< HEAD
     Az MDN közvetlen böngészése helyett az esetek többségében célszerűbb egy "MDN [kulcsszó]" alakú keresést indítani, például, ha a `parseInt` függvényről akarunk olvasni: <https://google.com/search?q=MDN+parseInt>.
 
 
 - **MSDN** – A Microsoft technikai dokumentáció gyűjteménye. Egyebek mellett JavaScript leírások is találhatóak rajta (többnyire JScript megnevezéssel). Internet Explorerrel kapcsolatos kérdések esetén a legjobb forrás. <http://msdn.microsoft.com/>.
 
     Az MDN-hez hasonlóan, itt is hatékonyabban kereshetünk közvetetten, például "RegExp MSDN" vagy "RegExp MSDN jscript".
+=======
+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.
+>>>>>>> 97ef86242f9f236b13152e1baf52a55c4db8728a
 
 ## Kompatibilitási táblázatok
 

1-js/02-first-steps/08-operators/article.md

@@ -104,7 +104,7 @@ Here's a more complex example:
 alert(2 + 2 + '1' ); // "41" and not "221"
 ```
 
-Here, operators work one after another. The first `+` sums two numbers, so it returns `4`, then the next `+` adds the string `1` to it, so it's like `4 + '1' = 41`.
+Here, operators work one after another. The first `+` sums two numbers, so it returns `4`, then the next `+` adds the string `1` to it, so it's like `4 + '1' = '41'`.
 
 ```js run
 alert('1' + 2 + 2); // "122" and not "14"
@@ -219,7 +219,7 @@ alert( x ); // 5
 
 The fact of `=` being an operator, not a "magical" language construct has an interesting implication.
 
-Most operators in JavaScript return a value. That's obvious for `+` and `-`, but also true for `=`.
+All operators in JavaScript return a value. That's obvious for `+` and `-`, but also true for `=`.
 
 The call `x = value` writes the `value` into `x` *and then returns it*.
 

1-js/02-first-steps/14-switch/article.md

@@ -47,7 +47,7 @@ switch (a) {
     break;
 */!*
   case 5:
-    alert( 'Too large' );
+    alert( 'Too big' );
     break;
   default:
     alert( "I don't know such values" );

1-js/02-first-steps/18-javascript-specials/article.md

@@ -273,7 +273,7 @@ We covered three ways to create a function in JavaScript:
     ```
 
 
-- Functions may have local variables: those declared inside its body. Such variables are only visible inside the function.
+- Functions may have local variables: those declared inside its body or its parameter list. Such variables are only visible inside the function.
 - Parameters can have default values: `function sum(a = 1, b = 2) {...}`.
 - Functions always return something. If there's no `return` statement, then the result is `undefined`.
 

1-js/03-code-quality/01-debugging-chrome/article.md

@@ -135,7 +135,7 @@ There are buttons for it at the top of the right panel. Let's engage them.
     Clicking this again and again will step through all script statements one by one.
 
 <span class="devtools" style="background-position:-62px -192px"></span> -- "Step over": run the next command, but *don't go into a function*, hotkey `key:F10`.
-: Similar to the previous the "Step" command, but behaves differently if the next statement is a function call. That is: not a built-in, like `alert`, but a function of our own.
+: Similar to the previous "Step" command, but behaves differently if the next statement is a function call. That is: not a built-in, like `alert`, but a function of our own.
 
     The "Step" command goes into it and pauses the execution at its first line, while "Step over" executes the nested function call invisibly, skipping the function internals.
 

1-js/03-code-quality/02-coding-style/article.md

@@ -116,7 +116,7 @@ There are two types of indents:
 
     One advantage of spaces over tabs is that spaces allow more flexible configurations of indents than the tab symbol.
 
-    For instance, we can align the arguments with the opening bracket, like this:
+    For instance, we can align the parameters with the opening bracket, like this:
 
     ```js no-beautify
     show(parameters,

1-js/03-code-quality/02-coding-style/code-style.svg

@@ -11,7 +11,7 @@ A good page to see the current state of support for language features is <https:
 
 As programmers, we'd like to use most recent features. The more good stuff - the better!
 
-From the other hand, how to make out modern code work on older engines that don't understand recent features yet?
+On the other hand, how to make our modern code work on older engines that don't understand recent features yet?
 
 There are two tools for that:
 

1-js/03-code-quality/06-polyfills/article.md

@@ -14,8 +14,8 @@ Simply put, "reachable" values are those that are accessible or usable somehow.
 
     For instance:
 
-    - Local variables and parameters of the current function.
-    - Variables and parameters for other functions on the current chain of nested calls.
+    - The currently executing function, its local variables and parameters.
+    - Other functions on the current chain of nested calls, their local variables and parameters.
     - Global variables.
     - (there are some other, internal ones as well)
 

1-js/04-object-basics/03-garbage-collection/article.md

@@ -15,6 +15,11 @@ describe("calculator", function() {
     afterEach(function() {
       prompt.restore();
     });
+    
+    it('the read get two values and saves them as object properties', function () {
+      assert.equal(calculator.a, 2);
+      assert.equal(calculator.b, 3);
+    });
 
     it("the sum is 5", function() {
       assert.equal(calculator.sum(), 5);

1-js/04-object-basics/04-object-methods/7-calculator/_js.view/test.js

@@ -10,6 +10,11 @@ describe("calculator", function() {
     calculator = new Calculator();
     calculator.read();
   });
+  
+  it("the read method asks for two values using prompt and remembers them in object properties", function() {
+    assert.equal(calculator.a, 2);
+    assert.equal(calculator.b, 3);
+  });
 
   it("when 2 and 3 are entered, the sum is 5", function() {
     assert.equal(calculator.sum(), 5);

1-js/04-object-basics/06-constructor-new/2-calculator-constructor/_js.view/test.js

@@ -91,7 +91,7 @@ The syntax from this section is rarely used, skip it unless you want to know eve
 
 Inside a function, we can check whether it was called with `new` or without it, using a special `new.target` property.
 
-It is empty for regular calls and equals the function if called with `new`:
+It is undefined for regular calls and equals the function if called with `new`:
 
 ```js run
 function User() {

1-js/04-object-basics/06-constructor-new/article.md

@@ -74,12 +74,12 @@ That's why the optional chaining `?.` was added to the language. To solve this p
 
 ## Optional chaining
 
-The optional chaining `?.` stops the evaluation if the part before `?.` is `undefined` or `null` and returns that part.
+The optional chaining `?.` stops the evaluation if the value before `?.` is `undefined` or `null` and returns `undefined`.
 
 **Further in this article, for brevity, we'll be saying that something "exists" if it's not `null` and not `undefined`.**
 
 In other words, `value?.prop`:
-- is the same as `value.prop` if `value` exists,
+- works as `value.prop`, if `value` exists,
 - otherwise (when `value` is `undefined/null`) it returns `undefined`.
 
 Here's the safe way to access `user.address.street` using `?.`:
@@ -103,7 +103,7 @@ alert( user?.address.street ); // undefined
 
 Please note: the `?.` syntax makes optional the value before it, but not any further.
 
-E.g. in `user?.address.street.name` the `?.` allows `user` to be `null/undefined`, but it's all it does. Further properties are accessed in a regular way. If we want some of them to be optional, then we'll need to replace more `.` with `?.`.
+E.g. in `user?.address.street.name` the `?.` allows `user` to safely be `null/undefined` (and returns `undefined` in that case), but that's only for `user`. Further properties are accessed in a regular way. If we want some of them to be optional, then we'll need to replace more `.` with `?.`.
 
 ```warn header="Don't overuse the optional chaining"
 We should use `?.` only where it's ok that something doesn't exist.
@@ -173,18 +173,16 @@ Then `?.()` checks the left part: if the admin function exists, then it runs (th
 The `?.[]` syntax also works, if we'd like to use brackets `[]` to access properties instead of dot `.`. Similar to previous cases, it allows to safely read a property from an object that may not exist.
 
 ```js run
+let key = "firstName";
+
 let user1 = {
   firstName: "John"
 };
 
-let user2 = null; // Imagine, we couldn't authorize the user
-
-let key = "firstName";
+let user2 = null; 
 
 alert( user1?.[key] ); // John
 alert( user2?.[key] ); // undefined
-
-alert( user1?.[key]?.something?.not?.existing); // undefined
 ```
 
 Also we can use `?.` with `delete`:

1-js/04-object-basics/07-optional-chaining/article.md

@@ -109,7 +109,7 @@ There will be no conflict between our and their identifiers, because symbols are
 
 ...But if we used a string `"id"` instead of a symbol for the same purpose, then there *would* be a conflict:
 
-```js run
+```js
 let user = { name: "John" };
 
 // Our script uses "id" property

1-js/04-object-basics/08-symbol/article.md

@@ -16,21 +16,29 @@ Imagine we need to write 1 billion. The obvious way is:
 let billion = 1000000000;
 ```
 
-But in real life, we usually avoid writing a long string of zeroes as it's easy to mistype. Also, we are lazy. We will usually write something like `"1bn"` for a billion or `"7.3bn"` for 7 billion 300 million. The same is true for most large numbers.
+We also can use underscore `_` as the separator:
 
-In JavaScript, we shorten a number by appending the letter `"e"` to the number and specifying the zeroes count:
+```js
+let billion = 1_000_000_000;
+```
+
+Here the underscore `_` plays the role of the "syntactic sugar", it makes the number more readable. The JavaScript engine simply ignores `_` between digits, so it's exactly the same one billion as above.
+
+In real life though, we try to avoid writing long sequences of zeroes. We're too lazy for that. We'll try to write something like `"1bn"` for a billion or `"7.3bn"` for 7 billion 300 million. The same is true for most large numbers.
+
+In JavaScript, we can shorten a number by appending the letter `"e"` to it and specifying the zeroes count:
 
 ```js run
 let billion = 1e9;  // 1 billion, literally: 1 and 9 zeroes
 
-alert( 7.3e9 );  // 7.3 billions (7,300,000,000)
+alert( 7.3e9 );  // 7.3 billions (same as 7300000000 or 7_300_000_000)
 ```
 
-In other words, `"e"` multiplies the number by `1` with the given zeroes count.
+In other words, `e` multiplies the number by `1` with the given zeroes count.
 
 ```js
-1e3 = 1 * 1000
-1.23e6 = 1.23 * 1000000
+1e3 = 1 * 1000 // e3 means *1000
+1.23e6 = 1.23 * 1000000 // e6 means *1000000
 ```
 
 Now let's write something very small. Say, 1 microsecond (one millionth of a second):
@@ -125,7 +133,7 @@ There are several built-in functions for rounding:
 : Rounds up: `3.1` becomes `4`, and `-1.1` becomes `-1`.
 
 `Math.round`
-: Rounds to the nearest integer: `3.1` becomes `3`, `3.6` becomes `4` and `-1.1` becomes `-1`.
+: Rounds to the nearest integer: `3.1` becomes `3`, `3.6` becomes `4`, the middle case: `3.5` rounds up to `4` too.
 
 `Math.trunc` (not supported by Internet Explorer)
 : Removes anything after the decimal point without rounding: `3.1` becomes `3`, `-1.1` becomes `-1`.

1-js/05-data-types/02-number/article.md

@@ -438,7 +438,7 @@ This operator has no special treatment for arrays, it works with them as with an
 Let's recall the rules:
 
 - Two objects are equal `==` only if they're references to the same object.
-- If one of arguments of `==` is an object, and the other one is a primitive, then the object gets converted to primitive, as explained in the chapter <info:object-toprimitive>.
+- If one of the arguments of `==` is an object, and the other one is a primitive, then the object gets converted to primitive, as explained in the chapter <info:object-toprimitive>.
 - ...With an exception of `null` and `undefined` that equal `==` each other and nothing else.
 
 The strict comparison `===` is even simpler, as it doesn't convert types. 

1-js/05-data-types/04-array/article.md

@@ -1,16 +1,14 @@
 function topSalary(salaries) {
 
-  let max = 0;
+  let maxSalary = 0;
   let maxName = null;
 
   for(const [name, salary] of Object.entries(salaries)) {
     if (max < salary) {
-      max = salary;
+      maxSalary = salary;
       maxName = name;
     }
   }
 
   return maxName;
-}
-
-
+}