Resolve conflicts / Update files on #186.

Author: odsantos

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

@@ -1,10 +1,6 @@
 # Uma Introdução ao JavaScript
 
-<<<<<<< HEAD
 Vamos ver o que há de tão especial no JavaScript, o que podemos fazer com ele, e que outras tecnologias funcionam bem com ele.
-=======
-Let's see what's so special about JavaScript, what we can achieve with it, and what other technologies play well with it.
->>>>>>> 0599d07b3c13ee25f583fc091cead3c17a7e7779
 
 ## O que é JavaScript?
 
@@ -71,13 +67,8 @@ Exemplos de tais restrições incluem:
 
     Os navegadores modernos permitem que ele trabalhe com arquivos, mas o acesso é limitado e fornecido apenas se o usuário executar determinadas ações, como "dropping" de um arquivo em uma janela do navegador ou selecioná-lo por meio de uma tag `<input>`.
 
-<<<<<<< HEAD
    Existem maneiras de interagir com a câmera / microfone e outros dispositivos, mas eles exigem permissão explícita do usuário. Assim, uma página habilitada para JavaScript pode não habilmente habilitar uma câmera web, observar os arredores e enviar as informações para a [NSA](https://pt.wikipedia.org/wiki/Ag%C3%AAncia_de_Seguran%C3%A7a_Nacional).
 - Diferentes abas/janelas geralmente não se conhecem mutuamente. Às vezes sim, por exemplo, quando uma janela usa JavaScript para abrir a outra. Mas mesmo neste caso, JavaScript de uma página pode não acessar a outra se eles vierem de sites diferentes (de um domínio, protocolo ou porta diferente).
-=======
-    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).
->>>>>>> 0599d07b3c13ee25f583fc091cead3c17a7e7779
 
     Isso é chamado de "Política de mesma origem ". Para contornar isso, *ambas as páginas* devem conter um código JavaScript especial que lida com a troca de dados.
 
@@ -125,12 +116,6 @@ Há mais. Claro que, mesmo que usemos uma dessas linguagens transpiladas, també
 
 ## Resumo
 
-<<<<<<< HEAD
 - O JavaScript foi inicialmente criado como uma linguagem somente de navegador, mas agora é usado em muitos outros ambientes também.
 - Hoje, o JavaScript tem uma posição única como a linguagem de navegador mais amplamente adotada, com integração total com HTML/CSS.
 - Existem muitas linguagens que são "transpiladas" para JavaScript e que oferecem certas funcionalidades. Recomenda-se dar uma olhada nelas, pelo menos brevemente, depois de dominar o JavaScript.
-=======
-- JavaScript was initially created as a browser-only language, but it is now used in many other environments as well.
-- Today, JavaScript has a unique position as the most widely-adopted browser language with full integration in HTML/CSS.
-- There are many languages that get "transpiled" to JavaScript and provide certain features. It is recommended to take a look at them, at least briefly, after mastering JavaScript.
->>>>>>> 0599d07b3c13ee25f583fc091cead3c17a7e7779

1-js/04-object-basics/01-object/8-multiply-numeric/task.md

@@ -1,16 +1,10 @@
-importância: 3
+importance: 3
 
 ---
 
-<<<<<<< HEAD
 # Multiplica as propriedades numéricas por 2
 
 Crie uma função `multiplyNumeric(obj)` que multiplique todas as propriedades numéricas de `obj` por `2`.
-=======
-# Multiply numeric property values by 2
-
-Create a function `multiplyNumeric(obj)` that multiplies all numeric property values of `obj` by `2`.
->>>>>>> 0599d07b3c13ee25f583fc091cead3c17a7e7779
 
 Por exemplo:
 

1-js/04-object-basics/02-object-copy/article.md

@@ -228,11 +228,6 @@ alert(clone.sizes.width); // 51, see the result from the other one
 
 To fix that, we should use the cloning loop that examines each value of `user[key]` and, if it's an object, then replicate its structure as well. That is called a "deep cloning".
 
-<<<<<<< HEAD
-There's a standard algorithm for deep cloning that handles the case above and more complex cases, called the [Structured cloning algorithm](https://html.spec.whatwg.org/multipage/structured-data.html#safe-passing-of-structured-data).
-
-=======
->>>>>>> e074a5f825a3d10b0c1e5e82561162f75516d7e3
 We can use recursion to implement it. Or, not to reinvent the wheel, take an existing implementation, for instance [_.cloneDeep(obj)](https://lodash.com/docs#cloneDeep) from the JavaScript library [lodash](https://lodash.com).
 
 ## Summary

1-js/04-object-basics/04-object-methods/article.md

@@ -15,7 +15,7 @@ Actions are represented in JavaScript by functions in properties.
 
 ## Method examples
 
-For the start, let's teach the `user` to say hello:
+For a start, let's teach the `user` to say hello:
 
 ```js run
 let user = {
@@ -63,11 +63,7 @@ user.sayHi(); // Hello!
 ```smart header="Object-oriented programming"
 When we write our code using objects to represent entities, that's called [object-oriented programming](https://en.wikipedia.org/wiki/Object-oriented_programming), in short: "OOP".
 
-<<<<<<< HEAD
-OOP is a big thing, an interesting science of its own. How to choose the right entities? How to organize the interaction between them? That's architecture, and there are great books on that topic, like "Design Patterns: Elements of Reusable Object-Oriented Software" by E.Gamma, R.Helm, R.Johnson, J.Vissides or "Object-Oriented Analysis and Design with Applications" by G.Booch, and more. 
-=======
 OOP is a big thing, an interesting science of its own. How to choose the right entities? How to organize the interaction between them? That's architecture, and there are great books on that topic, like "Design Patterns: Elements of Reusable Object-Oriented Software" by E. Gamma, R. Helm, R. Johnson, J. Vissides or "Object-Oriented Analysis and Design with Applications" by G. Booch, and more.
->>>>>>> e074a5f825a3d10b0c1e5e82561162f75516d7e3
 ```
 ### Method shorthand
 
@@ -76,14 +72,14 @@ There exists a shorter syntax for methods in an object literal:
 ```js
 // these objects do the same
 
-let user = {
+user = {
   sayHi: function() {
     alert("Hello");
   }
 };
 
 // method shorthand looks better, right?
-let user = {
+user = {
 *!*
   sayHi() { // same as "sayHi: function()"
 */!*
@@ -115,6 +111,7 @@ let user = {
 
   sayHi() {
 *!*
+    // "this" is the "current object"
     alert(this.name);
 */!*
   }
@@ -172,15 +169,7 @@ If we used `this.name` instead of `user.name` inside the `alert`, then the code
 
 ## "this" is not bound
 
-<<<<<<< HEAD
-<<<<<<< HEAD
-In JavaScript, "this" keyword behaves unlike most other programming languages. First, it can be used in any function.
-=======
-In JavaScript, keyword `this` behaves unlike most other programming languages. It can be used in any function.
->>>>>>> e074a5f825a3d10b0c1e5e82561162f75516d7e3
-=======
 In JavaScript, keyword `this` behaves unlike most other programming languages. It can be used in any function, even if it's not a method of an object.
->>>>>>> 0599d07b3c13ee25f583fc091cead3c17a7e7779
 
 There's no syntax error in the following example:
 
@@ -190,9 +179,9 @@ function sayHi() {
 }
 ```
 
-The value of `this` is evaluated during the run-time. And it can be anything.
+The value of `this` is evaluated during the run-time, depending on the context.
 
-For instance, the same function may have different "this" when called from different objects:
+For instance, here the same function is assigned to two different objects and has different "this" in the calls:
 
 ```js run
 let user = { name: "John" };
@@ -203,7 +192,7 @@ function sayHi() {
 }
 
 *!*
-// use the same functions in two objects
+// use the same function in two objects
 user.f = sayHi;
 admin.f = sayHi;
 */!*
@@ -216,7 +205,10 @@ admin.f(); // Admin  (this == admin)
 admin['f'](); // Admin (dot or square brackets access the method – doesn't matter)
 ```
 
-Actually, we can call the function without an object at all:
+The rule is simple: if `obj.f()` is called, then `this` is `obj` during the call of `f`. So it's either `user` or `admin` in the example above.
+
+````smart header="Calling without an object: `this == undefined`"
+We can even call the function without an object at all:
 
 ```js run
 function sayHi() {
@@ -230,12 +222,8 @@ In this case `this` is `undefined` in strict mode. If we try to access `this.nam
 
 In non-strict mode the value of `this` in such case will be the *global object* (`window` in a browser, we'll get to it later in the chapter [](info:global-object)). This is a historical behavior that `"use strict"` fixes.
 
-<<<<<<< HEAD
-Please note that usually a call of a function that uses `this` without an object is not normal, but rather a programming mistake. If a function has `this`, then it is usually meant to be called in the context of an object.
-=======
 Usually such call is a programming error. If there's `this` inside a function, it expects to be called in an object context.
 ````
->>>>>>> e074a5f825a3d10b0c1e5e82561162f75516d7e3
 
 ```smart header="The consequences of unbound `this`"
 If you come from another programming language, then you are probably used to the idea of a "bound `this`", where methods defined in an object always have `this` referencing that object.
@@ -247,99 +235,6 @@ The concept of run-time evaluated `this` has both pluses and minuses. On the one
 Here our position is not to judge whether this language design decision is good or bad. We'll understand how to work with it, how to get benefits and avoid problems.
 ```
 
-<<<<<<< HEAD
-## Internals: Reference Type
-
-```warn header="In-depth language feature"
-This section covers an advanced topic, to understand certain edge-cases better.
-
-If you want to go on faster, it can be skipped or postponed.
-```
-
-An intricate method call can lose `this`, for instance:
-
-```js run
-let user = {
-  name: "John",
-  hi() { alert(this.name); },
-  bye() { alert("Bye"); }
-};
-
-user.hi(); // John (the simple call works)
-
-*!*
-// now let's call user.hi or user.bye depending on the name
-(user.name == "John" ? user.hi : user.bye)(); // Error!
-*/!*
-```
-
-On the last line there is a ternary operator that chooses either `user.hi` or `user.bye`. In this case the result is `user.hi`.
-
-The method is immediately called with parentheses `()`. But it doesn't work right!
-
-You can see that the call results in an error, because the value of `"this"` inside the call becomes `undefined`.
-
-This works (object dot method):
-```js
-user.hi();
-```
-
-This doesn't (evaluated method):
-```js
-(user.name == "John" ? user.hi : user.bye)(); // Error!
-```
-
-Why? If we want to understand why it happens, let's get under the hood of how `obj.method()` call works.
-
-Looking closely, we may notice two operations in `obj.method()` statement:
-
-1. First, the dot `'.'` retrieves the property `obj.method`.
-2. Then parentheses `()` execute it.
-
-So, how does the information about `this` get passed from the first part to the second one?
-
-If we put these operations on separate lines, then `this` will be lost for sure:
-
-```js run
-let user = {
-  name: "John",
-  hi() { alert(this.name); }
-}
-
-*!*
-// split getting and calling the method in two lines
-let hi = user.hi;
-hi(); // Error, because this is undefined
-*/!*
-```
-
-Here `hi = user.hi` puts the function into the variable, and then on the last line it is completely standalone, and so there's no `this`.
-
-**To make `user.hi()` calls work, JavaScript uses a trick -- the dot `'.'` returns not a function, but a value of the special [Reference Type](https://tc39.github.io/ecma262/#sec-reference-specification-type).**
-
-The Reference Type is a "specification type". We can't explicitly use it, but it is used internally by the language.
-
-The value of Reference Type is a three-value combination `(base, name, strict)`, where:
-
-- `base` is the object.
-- `name` is the property.
-- `strict` is true if `use strict` is in effect.
-
-The result of a property access `user.hi` is not a function, but a value of Reference Type. For `user.hi` in strict mode it is:
-
-```js
-// Reference Type value
-(user, "hi", true)
-```
-
-When parentheses `()` are called on the Reference Type, they receive the full information about the object and its method, and can set the right `this` (`=user` in this case).
-
-Any other operation like assignment `hi = user.hi` discards the reference type as a whole, takes the value of `user.hi` (a function) and passes it on. So any further operation "loses" `this`.
-
-So, as the result, the value of `this` is only passed the right way if the function is called directly using a dot `obj.method()` or square brackets `obj['method']()` syntax (they do the same here). Later in this tutorial, we will learn various ways to solve this problem such as [func.bind()](/bind#solution-2-bind).
-
-=======
->>>>>>> e074a5f825a3d10b0c1e5e82561162f75516d7e3
 ## Arrow functions have no "this"
 
 Arrow functions are special: they don't have their "own" `this`. If we reference `this` from such a function, it's taken from the outer "normal" function.
@@ -369,7 +264,7 @@ That's a special feature of arrow functions, it's useful when we actually do not
 
 The value of `this` is defined at run-time.
 - When a function is declared, it may use `this`, but that `this` has no value until the function is called.
-- That function can be copied between objects.
+- A function can be copied between objects.
 - When a function is called in the "method" syntax: `object.method()`, the value of `this` during the call is `object`.
 
 Please note that arrow functions are special: they have no `this`. When `this` is accessed inside an arrow function, it is taken from outside.

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

@@ -44,12 +44,7 @@ AND'ing the whole path to the property ensures that all components exist (if not
 
 The optional chaining `?.` stops the evaluation and returns `undefined` if the part before `?.` is `undefined` or `null`.
 
-<<<<<<< HEAD
-Further in this article, for brevity, we'll be saying that something "exists" if it's not `null` and not `undefined`.
-
-=======
 **Further in this article, for brevity, we'll be saying that something "exists" if it's not `null` and not `undefined`.**
->>>>>>> e074a5f825a3d10b0c1e5e82561162f75516d7e3
 
 Here's the safe way to access `user.address.street`:
 
@@ -65,16 +60,6 @@ Reading the address with `user?.address` works even if `user` object doesn't exi
 let user = null;
 
 alert( user?.address ); // undefined
-<<<<<<< HEAD
-
-alert( user?.address.street ); // undefined
-alert( user?.address.street.anything ); // undefined
-```
-
-Please note: the `?.` syntax works exactly where it's placed, not any further.
-
-In the last two lines the evaluation stops immediately after `user?.`, never accessing further properties. But if the `user` actually exists, then the further intermediate properties, such as `user.address` must exist.
-=======
 alert( user?.address.street ); // undefined
 ```
 
@@ -83,7 +68,6 @@ Please note: the `?.` syntax makes optional the value before it, but not any fur
 In the example above, `user?.` allows only `user` to be `null/undefined`.
 
 On the other hand, if `user` does exist, then it must have `user.address` property, otherwise `user?.address.street` gives an error at the second dot.
->>>>>>> e074a5f825a3d10b0c1e5e82561162f75516d7e3
 
 ```warn header="Don't overuse the optional chaining"
 We should use `?.` only where it's ok that something doesn't exist.
@@ -93,27 +77,14 @@ For example, if according to our coding logic `user` object must be there, but `
 So, if `user` happens to be undefined due to a mistake, we'll see a programming error about it and fix it. Otherwise, coding errors can be silenced where not appropriate, and become more difficult to debug.
 ```
 
-<<<<<<< HEAD
-````warn header="The variable before `?.` must exist"
-If there's no variable `user`, then `user?.anything` triggers an error:
-=======
 ````warn header="The variable before `?.` must be declared"
 If there's no variable `user` at all, then `user?.anything` triggers an error:
->>>>>>> e074a5f825a3d10b0c1e5e82561162f75516d7e3
 
 ```js run
 // ReferenceError: user is not defined
 user?.address;
 ```
-<<<<<<< HEAD
-<<<<<<< HEAD
-The optional chaining only tests for `null/undefined`, doesn't interfere with any other language mechanics.
-=======
-There must be `let/const/var user`. The optional chaining works only for declared variables.
->>>>>>> e074a5f825a3d10b0c1e5e82561162f75516d7e3
-=======
 There must be a declaration (e.g. `let/const/var user`). The optional chaining works only for declared variables.
->>>>>>> 0599d07b3c13ee25f583fc091cead3c17a7e7779
 ````
 
 ## Short-circuiting
@@ -158,15 +129,7 @@ user2.admin?.();
 
 Here, in both lines we first use the dot (`user1.admin`) to get `admin` property, because the user object must exist, so it's safe read from it.
 
-<<<<<<< HEAD
-<<<<<<< HEAD
-Then `?.()` checks the left part: if the user exists, then it runs (for `user1`). Otherwise (for `user2`) the evaluation stops without errors.
-=======
-Then `?.()` checks the left part: if the admin function exists, then it runs (for `user1`). Otherwise (for `user2`) the evaluation stops without errors.
->>>>>>> e074a5f825a3d10b0c1e5e82561162f75516d7e3
-=======
 Then `?.()` checks the left part: if the admin function exists, then it runs (that's so for `user1`). Otherwise (for `user2`) the evaluation stops without errors.
->>>>>>> 0599d07b3c13ee25f583fc091cead3c17a7e7779
 
 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.