Merge pull request #196 from javascript-tutorial/sync-23da191b

Sync with upstream @ 23da191

Author: odsantos

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

@@ -9,7 +9,7 @@ Então, primeiro, vamos ver como anexar um script a uma página. Para ambientes
 
 ## A tag "script"
 
-Os programas JavaScript podem ser inseridos em qualquer parte de um documento HTML com a ajuda da tag `<script>`.
+Os programas JavaScript podem ser inseridos em quase qualquer parte de um documento HTML com a ajuda da tag `<script>`.
 
 Por exemplo:
 

1-js/04-object-basics/01-object/article.md

@@ -92,30 +92,6 @@ let user = {
 ```
 Esta é chamada de vírgula à direita (*trailing comma*) ou "vírgula pendurada" (*hanging comma*). Ela facilita o adicionar/remover/mover propriedades, porque todas as linhas se tornam semelhantes.
 
-````smart header="Objeto com const pode ser alterado"
-Por favor, note: um objeto declarado como `const` *pode* ser modificado.
-
-Por exemplo:
-
-```js run
-const user = {
-  name: "John"
-};
-
-*!*
-user.name = "Pete"; // (*)
-*/!*
-
-alert(user.name); // Pete
-```
-
-Poderá parecer que a linha `(*)` irá causar um erro, mas não. A `const` fixa o valor de `user`, mas não o seu conteúdo.
-
-A `const` dará um erro apenas se tentarmos mudar `user=...` como um todo.
-
-Há outra forma para tornar constantes as propriedades de um objeto, que iremos ver mais adiante no capítulo <info:property-descriptors>.
-````
-
 ## Parênteses retos
 
 Para propriedades com múltiplas palavras, o acesso por ponto não funciona:

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

@@ -73,7 +73,6 @@ admin.name = 'Pete'; // changed by the "admin" reference
 alert(*!*user.name*/!*); // 'Pete', changes are seen from the "user" reference
 ```
 
-
 It's just as if we had a cabinet with two keys and used one of them (`admin`) to get into it. Then, if we later use another key (`user`) we can see changes.
 
 ## Comparison by reference
@@ -230,6 +229,30 @@ To fix that, we should use the cloning loop that examines each value of `user[ke
 
 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).
 
+```smart header="Const objects can be modified"
+An important "side effect" of storing objects as references is that an object declared as `const` *can* be modified.
+
+For instance:
+
+```js run
+const user = {
+  name: "John"
+};
+
+*!*
+user.name = "Pete"; // (*)
+*/!*
+
+alert(user.name); // Pete
+```
+
+It might seem that the line `(*)` would cause an error, but no. The value of `user` is constant, it must always reference the same object. But properties of that object are free to change.
+
+In other words, the `const user` gives an error only if we try to set `user=...` as a whole, and that's all.
+
+That said, if we really need to make constant object properties, it's also possible, but using totally different methods, we'll mention that in the chapter <info:property-descriptors>.
+```
+
 ## Summary
 
 Objects are assigned and copied by reference. In other words, a variable stores not the "object value", but a "reference" (address in memory) for the value. So copying such a variable or passing it as a function argument copies that reference, not the object.

2-ui/4-forms-controls/3-events-change-input/article.md

@@ -62,11 +62,15 @@ For instance, the code below prevents all such events and shows what we are tryi
 </script>
 ```
 
-Technically, we can copy/paste everything. For instance, we can copy a file in the OS file manager, and paste it.
+Please note, that it's possible to copy/paste not just text, but everything. For instance, we can copy a file in the OS file manager, and paste it.
 
-There's a list of methods [in the specification](https://www.w3.org/TR/clipboard-apis/#dfn-datatransfer) to work with different data types, read/write to the clipboard.
+That's because `clipboardData` implements `DataTransfer` interface, commonly used for drag'n'drop and copy/pasting. It's bit beyound our scope now, but you can find its methods [in the specification](https://html.spec.whatwg.org/multipage/dnd.html#the-datatransfer-interface).
 
-But please note that clipboard is a "global" OS-level thing. Most browsers allow read/write access to the clipboard only in the scope of certain user actions for the safety. Also it is forbidden to create "custom" clipboard events in all browsers except Firefox.
+```warn header="ClipboardAPI: user safety restrictions"
+The clipboard is a "global" OS-level thing. So most browsers allow read/write access to the clipboard only in the scope of certain user actions for the safety, e.g. in `onclick` event handlers.
+
+Also it's forbidden to generate "custom" clipboard events with `dispatchEvent` in all browsers except Firefox.
+```
 
 ## Summary