(253-1) (que é `9007199254740991`) ou menores que -( 253-1) para negativos.
Para ser realmente preciso, o tipo "number" pode armazenar números inteiros maiores (até 1.7976931348623157 * 10308), mas fora do intervalo de números inteiros seguros ±(2 53-1) haverá um erro de precisão, porque nem todos os dígitos cabem no armazenamento fixo de 64 bits. Portanto, um valor “aproximado” pode ser armazenado.
+=======
+In JavaScript, the "number" type cannot safely represent integer values larger than (253-1) (that's `9007199254740991`), or less than -(253-1) for negatives.
+
+To be really precise, the "number" type can store larger integers (up to 1.7976931348623157 * 10308), but outside of the safe integer range ±(253-1) there'll be a precision error, because not all digits fit into the fixed 64-bit storage. So an "approximate" value may be stored.
+
+For example, these two numbers (right above the safe range) are the same:
+
+```js
+console.log(9007199254740991 + 1); // 9007199254740992
+console.log(9007199254740991 + 2); // 9007199254740992
+```
+
+So to say, all odd integers greater than (253-1) can't be stored at all in the "number" type.
+
+For most purposes ±(253-1) range is quite enough, but sometimes we need the entire range of really big integers, e.g. for cryptography or microsecond-precision timestamps.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Por exemplo, estes dois números (logo acima da faixa segura) são iguais:
@@ -94,12 +111,15 @@ const bigInt = 1234567890123456789012345678901234567890n;
Como os números `BigInt` raramente são necessários, nós não os cobrimos aqui, mas dedicamos-lhes um capítulo separado ±(253-1).
- `bigint` é para números inteiros de comprimento arbitrário.
- `string` para cadeias-de-caracteres. Uma *string* pode ter zero ou mais caracteres, não há nenhum tipo de caractere único separado.
@@ -281,6 +306,18 @@ Existem 8 tipos básicos em JavaScript.
- `undefined` para valores não atribuídos -- um tipo autônomo que tem um único valor `undefined`.
- `object` para estruturas de dados mais complexas.
- `symbol` para identificadores exclusivos.
+=======
+- Seven primitive data types:
+ - `number` for numbers of any kind: integer or floating-point, integers are limited by ±(253-1).
+ - `bigint` for integer numbers of arbitrary length.
+ - `string` for strings. A string may have zero or more characters, there's no separate single-character type.
+ - `boolean` for `true`/`false`.
+ - `null` for unknown values -- a standalone type that has a single value `null`.
+ - `undefined` for unassigned values -- a standalone type that has a single value `undefined`.
+ - `symbol` for unique identifiers.
+- And one non-primitive data type:
+ - `object` for more complex data structures.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
O operador `typeof` nos permite ver que tipo está armazenado em uma variável.
diff --git a/1-js/02-first-steps/07-type-conversions/article.md b/1-js/02-first-steps/07-type-conversions/article.md
index 88f14e8ac..12d46b8fc 100644
--- a/1-js/02-first-steps/07-type-conversions/article.md
+++ b/1-js/02-first-steps/07-type-conversions/article.md
@@ -6,8 +6,13 @@ Por exemplo, `alert` converte automaticamente qualquer valor para string antes d
Também existem casos em que precisamos explicitamente de converter um valor para o tipo que precisamos.
+<<<<<<< HEAD
```smart header="Não vamos falar de objetos"
Nesse capítulo, não vamos falar sobre objetos. Por agora, vamos abordar apenas os tipos primitivos.
+=======
+```smart header="Not talking about objects yet"
+In this chapter, we won't cover objects. For now, we'll just be talking about primitives.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Mais tarde, após abordarmos objetos no capítulo true e false| `1` e `0` |
| `string` | Espaços em branco do início e do fim são removidos. Se a string que sobrar for vazia, o resultado é `0`. Senão, o número é "lido" a partir da string. Um erro nos dá `NaN`|
+=======
+|true and false | `1` and `0` |
+| `string` | Whitespaces (includes spaces, tabs `\t`, newlines `\n` etc.) from the start and end are removed. If the remaining string is empty, the result is `0`. Otherwise, the number is "read" from the string. An error gives `NaN`. |
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Exemplos:
@@ -129,8 +145,13 @@ A conversão segue as seguintes regras:
|-------|-------------|
|`undefined`|`NaN`|
|`null`|`0`|
+<<<<<<< HEAD
|true / false| `1 / 0` |
| `string` | A string é lida "como ela é", espaços em branco do início e do fim são ignorados. Uma string vazia, vira `0`. Um erro nos dá `NaN`|
+=======
+|true / false | `1 / 0` |
+| `string` | The string is read "as is", whitespaces (includes spaces, tabs `\t`, newlines `\n` etc.) from both sides are ignored. An empty string becomes `0`. An error gives `NaN`. |
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
**`Conversões Booleanas`** -- Ocorrem em operações lógicas. Podem ser feitas com `Boolean(value)`.
diff --git a/1-js/02-first-steps/08-operators/3-primitive-conversions-questions/solution.md b/1-js/02-first-steps/08-operators/3-primitive-conversions-questions/solution.md
index 114984580..7a1f7903b 100644
--- a/1-js/02-first-steps/08-operators/3-primitive-conversions-questions/solution.md
+++ b/1-js/02-first-steps/08-operators/3-primitive-conversions-questions/solution.md
@@ -16,6 +16,7 @@ undefined + 1 = NaN // (6)
" \t \n" - 2 = -2 // (7)
```
+<<<<<<< HEAD
1. A adição de uma string `"" + 1` converte `1` para uma string: `"" + 1 = "1"`, e quando nós temos `"1" + 0`, a mesma regra é aplicada.
2. A subtração `-` (como a maioria das operações matemáticas) apenas funciona com números, e converte uma string vazia `""` para `0`.
3. A adição a uma string anexa o número `5` à string.
@@ -23,3 +24,12 @@ undefined + 1 = NaN // (6)
5. `null` se torna `0` após a conversão numérica.
6. `undefined` se torna `NaN` após a conversão numérica.
7. Caracteres de espaço, são aparados do início e final de uma string quando esta é convertida em um número. Aqui a string inteira consiste em caracteres de espaço, tais como `\t`, `\n` e um espaço "regular" entre eles. Então, similarmente à string vazia, isto se torna `0`.
+=======
+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`.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
diff --git a/1-js/02-first-steps/08-operators/article.md b/1-js/02-first-steps/08-operators/article.md
index 4c5e9116b..d24f14d75 100644
--- a/1-js/02-first-steps/08-operators/article.md
+++ b/1-js/02-first-steps/08-operators/article.md
@@ -50,8 +50,14 @@ O resultado de `a % b` é o [resto](https://pt.wikipedia.org/wiki/Resto_da_divis
Por exemplo:
```js run
+<<<<<<< HEAD
alert( 5 % 2 ); // 1, o resto de 5 dividido por 2
alert( 8 % 3 ); // 2, o resto de 8 dividido por 3
+=======
+alert( 5 % 2 ); // 1, the remainder of 5 divided by 2
+alert( 8 % 3 ); // 2, the remainder of 8 divided by 3
+alert( 8 % 4 ); // 0, the remainder of 8 divided by 4
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
```
### Exponenciação **
@@ -68,7 +74,11 @@ alert( 2 ** 3 ); // 2³ = 8
alert( 2 ** 4 ); // 2⁴ = 16
```
+<<<<<<< HEAD
Assim como na matemática, o operador de exponenciação também é definido para números não-inteiros.
+=======
+Just like in maths, the exponentiation operator is defined for non-integer numbers as well.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Por exemplo, a raiz quadrada é uma exponenciação por ½:
@@ -80,7 +90,11 @@ alert( 8 ** (1/3) ); // 2 (a potência de 1/3 é o mesmo que a raiz cúbica)
## Concatenação de strings com + binário
+<<<<<<< HEAD
Vamos conhecer os recursos dos operadores JavaScript que estão para além da aritmética escolar.
+=======
+Let's meet the features of JavaScript operators that are beyond school arithmetics.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Normalmente o operador mais `+` soma números.
@@ -194,6 +208,7 @@ Aqui está um extrato da [tabela de precedência](https://developer.mozilla.org/
| Precedência | Nome | Sinal |
|------------|------|------|
| ... | ... | ... |
+<<<<<<< HEAD
| 15 | positivo unário | `+` |
| 15 | negativo unário | `-` |
| 14 | exponenciação | `**` |
@@ -201,11 +216,24 @@ Aqui está um extrato da [tabela de precedência](https://developer.mozilla.org/
| 13 | divisão | `/` |
| 12 | adição | `+` |
| 12 | subtração | `-` |
+=======
+| 14 | unary plus | `+` |
+| 14 | unary negation | `-` |
+| 13 | exponentiation | `**` |
+| 12 | multiplication | `*` |
+| 12 | division | `/` |
+| 11 | addition | `+` |
+| 11 | subtraction | `-` |
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
| ... | ... | ... |
| 2 | atribuição | `=` |
| ... | ... | ... |
+<<<<<<< HEAD
Como podemos ver, o "positivo unário" tem uma prioridade de `15` que é maior que a de `12` da "adição" (positivo binário). É por este motivo que na expressão `"+apples + +oranges"`, positivos unários operam antes da adição.
+=======
+As we can see, the "unary plus" has a priority of `14` which is higher than the `11` of "addition" (binary plus). That's why, in the expression `"+apples + +oranges"`, unary pluses work before the addition.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
## Atribuição
@@ -303,7 +331,11 @@ Tais operadores têm a mesma precedência que uma atribuição normal, de modo q
```js run
let n = 2;
+<<<<<<< HEAD
n *= 3 + 5; // parte à direita avaliada primeiro, o mesmo que n *= 8
+=======
+n *= 3 + 5; // right part evaluated first, same as n *= 8
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
alert( n ); // 16
```
@@ -437,7 +469,11 @@ A lista de operadores:
- RIGHT SHIFT ( `>>` )
- ZERO-FILL RIGHT SHIFT ( `>>>` )
+<<<<<<< HEAD
Estes operadores são muito raramente usados, e acontece quando nós precisamos mexer com números no nível mais baixo (bit a bit). Nós não precisaremos destes operadores tão cedo, já que desenvolvimento web faz pouco uso deles, mas em algumas áreas específicas, como em criptografia, eles são úteis. Você pode ler o capítulo [Operadores bit a bit](https://developer.mozilla.org/pt-BR/docs/Web/JavaScript/Guide/Expressions_and_Operators#operadores_bit_a_bit) na MDN quando surgir a necessidade.
+=======
+These operators are used very rarely, when we need to fiddle with numbers on the very lowest (bitwise) level. We won't need these operators any time soon, as web development has little use of them, but in some special areas, such as cryptography, they are useful. You can read the [Bitwise Operators](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Expressions_and_Operators#bitwise_operators) chapter on MDN when a need arises.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
## Vírgula
diff --git a/1-js/02-first-steps/10-ifelse/article.md b/1-js/02-first-steps/10-ifelse/article.md
index e4d5c8076..c576d9395 100644
--- a/1-js/02-first-steps/10-ifelse/article.md
+++ b/1-js/02-first-steps/10-ifelse/article.md
@@ -68,9 +68,13 @@ if (cond) {
## A cláusula "else"
+<<<<<<< HEAD
A instrução `if` pode conter um bloco opcional "else" (senão). Ele é executado quando a condição é falsa.
Por exemplo:
+=======
+The `if` statement may contain an optional `else` block. It executes when the condition is falsy.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
```js run
let year = prompt('Em que ano foi publicada a especificação ECMAScript-2015?', '');
@@ -183,10 +187,17 @@ alert( message );
Pode ser difícil no início entender o que está acontecendo. Mas depois de um olhar mais atento, percebemos que é apenas uma sequência comum de testes:
+<<<<<<< HEAD
1. O primeiro ponto de interrogação verifica se `age < 3`.
2. Se for verdadeiro -- retorna `'Oi, bebê!'`. Caso contrário, continua para a expressão após os dois pontos ":", verificando `age < 18`.
3. Se for verdade -- retorna `'Olá!'`. Caso contrário, continua para a expressão após os próximos dois pontos ":", verificando `age < 100`.
4. Se for verdade -- retorna `'Saudações!'`. Caso contrário, continua com a expressão após os últimos dois-pontos ":", retornando `'Que idade incomum!'`.
+=======
+1. The first question mark checks whether `age < 3`.
+2. If true -- it returns `'Hi, baby!'`. Otherwise, it continues to the expression after the colon ":", checking `age < 18`.
+3. If that's true -- it returns `'Hello!'`. Otherwise, it continues to the expression after the next colon ":", checking `age < 100`.
+4. If that's true -- it returns `'Greetings!'`. Otherwise, it continues to the expression after the last colon ":", returning `'What an unusual age!'`.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Veja como isso fica usando `if..else`:
diff --git a/1-js/02-first-steps/12-nullish-coalescing-operator/article.md b/1-js/02-first-steps/12-nullish-coalescing-operator/article.md
index f9733a0fe..ad751dc14 100644
--- a/1-js/02-first-steps/12-nullish-coalescing-operator/article.md
+++ b/1-js/02-first-steps/12-nullish-coalescing-operator/article.md
@@ -4,7 +4,11 @@
O operador de coalescência nula é escrito usando dois sinais de interrogação `??`.
+<<<<<<< HEAD
Como ele trata `null` e `undefined` da mesma forma, nós iremos usar um termo especial aqui, neste artigo. Diremos que uma expressão está definida quando não é `null` nem `undefined`.
+=======
+As it treats `null` and `undefined` similarly, we'll use a special term here, in this article. For brevity, we'll say that a value is "defined" when it's neither `null` nor `undefined`.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
O resultado de `a ?? b` é:
@@ -23,14 +27,24 @@ result = a !== null && a !== undefined ? a : b;
Agora, deveria estar completamente claro o que `??` faz. Vamos ver onde ele é útil.
+<<<<<<< HEAD
O caso de uso comum para `??` é obter um valor padrão para uma variável potencialmente indefinida.
Por exemplo, aqui exibimos `Anônimo` se `user` não for definido:
+=======
+The common use case for `??` is to provide a default value.
+
+For example, here we show `user` if its value isn't `null/undefined`, otherwise `Anonymous`:
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
```js run
let user;
+<<<<<<< HEAD
alert(user ?? "Anônimo"); // Anônimo ("user" não definido)
+=======
+alert(user ?? "Anonymous"); // Anonymous (user is undefined)
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
```
Aqui está o exemplo com um nome atribuído a `user`:
@@ -38,14 +52,24 @@ Aqui está o exemplo com um nome atribuído a `user`:
```js run
let user = "João";
+<<<<<<< HEAD
alert(user ?? "Anônimo"); // João ("user" está definido)
+=======
+alert(user ?? "Anonymous"); // John (user is not null/undefined)
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
```
Podemos também usar uma sequência de `??` para selecionar o primeiro valor em uma lista que não seja `null/undefined`.
+<<<<<<< HEAD
Digamos que temos dados de um usuário nas variáveis `nome`, `sobrenome` ou `apelido`. Todos eles podem ser indefinidos, se o usuário optar por não entrar com um valor.
Gostaríamos de exibir o nome do usuário usando uma dessas variáveis, ou exibir "Anônimo" se todas elas forem indefinidas.
+=======
+Let's say we have a user's data in variables `firstName`, `lastName` or `nickName`. All of them may be not defined, if the user decided not to fill in the corresponding values.
+
+We'd like to display the user name using one of these variables, or show "Anonymous" if all of them are `null/undefined`.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Para isso usaremos o operador `??`:
@@ -77,7 +101,11 @@ alert(firstName || lastName || nickName || "Anônimo"); // Supercoder
*/!*
```
+<<<<<<< HEAD
Historicamente, o operador OU `||` foi o primeiro a existir. Ele existe desde a criação do JavaScript, e vem sendo utilizado para este propósito desde então.
+=======
+Historically, the OR `||` operator was there first. It's been there since the beginning of JavaScript, so developers were using it for such purposes for a long time.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Por outro lado, o operador de coalescência nula `??` foi adicionado ao JavaScript recentemente, e a razão para isso foi o descontentamento com `||`.
@@ -108,11 +136,19 @@ Na prática, a altura igual a zero é um valor válido que não deve ser substit
## Precedência
+<<<<<<< HEAD
A precedência do operador `??` é a mesma que a de `||`. Ambos são iguais a '4' na [tabela MDN](https://developer.mozilla.org/pt-BR/docs/Web/JavaScript/Reference/Operators/Operator_Precedence#Table).
+=======
+The precedence of the `??` operator is the same as `||`. They both equal `3` in the [MDN table](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence#Table).
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Isto significa que, tal como `||`, o operador de coalescência nula `??` é avaliado antes de `=` e `?`, mas após a maioria dos outros operadores, como `+` e `*`.
+<<<<<<< HEAD
Então, se quiser selecionar um valor com `??` em uma expressão com outros operadores, considere o uso de parênteses:
+=======
+So we may need to add parentheses in expressions like this:
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
```js run
let height = null;
@@ -130,8 +166,13 @@ Caso contrário, se omitirmos os parênteses, como `*` tem maior precedência qu
// sem parênteses
let area = height ?? 100 * width ?? 50;
+<<<<<<< HEAD
// ...funciona desta forma (provavelmente não como gostaríamos):
let area = height ?? 100 * width ?? 50;
+=======
+// ...works this way (not what we want):
+let area = height ?? (100 * width) ?? 50;
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
```
### Usando ?? com && ou ||
diff --git a/1-js/02-first-steps/14-switch/article.md b/1-js/02-first-steps/14-switch/article.md
index a661d7d0a..7200c3ed7 100644
--- a/1-js/02-first-steps/14-switch/article.md
+++ b/1-js/02-first-steps/14-switch/article.md
@@ -139,7 +139,11 @@ switch (a) {
Agora ambos `3` e `5` mostram a mesma mensagem.
+<<<<<<< HEAD
A habilidade para "agrupar" cases é um efeito secundário de como o `switch/case` funciona sem `break`. Aqui a execução do `case 3` começa pela linha `(*)` e prossegue pelo `case 5`, por não existir `break`.
+=======
+The ability to "group" cases is a side effect of how `switch/case` works without `break`. Here the execution of `case 3` starts from the line `(*)` and goes through `case 5`, because there's no `break`.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
## O tipo de dados importa
diff --git a/1-js/02-first-steps/15-function-basics/1-if-else-required/solution.md b/1-js/02-first-steps/15-function-basics/1-if-else-required/solution.md
index b7c045d0b..7ba3ca286 100644
--- a/1-js/02-first-steps/15-function-basics/1-if-else-required/solution.md
+++ b/1-js/02-first-steps/15-function-basics/1-if-else-required/solution.md
@@ -1,3 +1,9 @@
+<<<<<<< HEAD
Nenhuma diferença!
-Em ambos os casos, `return confirm('Seus pais permitiram?')` é executado exatamente quando a condição `if` é falsa.
\ No newline at end of file
+Em ambos os casos, `return confirm('Seus pais permitiram?')` é executado exatamente quando a condição `if` é falsa.
+=======
+No difference!
+
+In both cases, `return confirm('Did parents allow you?')` executes exactly when the `if` condition is falsy.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
diff --git a/1-js/02-first-steps/15-function-basics/article.md b/1-js/02-first-steps/15-function-basics/article.md
index 461d4978a..8b90d0cdb 100644
--- a/1-js/02-first-steps/15-function-basics/article.md
+++ b/1-js/02-first-steps/15-function-basics/article.md
@@ -24,7 +24,11 @@ A palavra-chave `function` vem primeiro, depois vem o *nome da função*, e uma
```js
function name(parameter1, parameter2, ... parameterN) {
+<<<<<<< HEAD
...corpo...
+=======
+ // body
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
}
```
@@ -175,8 +179,13 @@ Quando um valor é passado como um parâmetro de função, ele também é chamad
Em outras palavras, para colocar esses termos em ordem:
+<<<<<<< HEAD
- Um parâmetro é a variável listada entre parênteses na declaração da função (é um termo de tempo de declaração)
- Um argumento é o valor passado para a função quando ela é chamada (é um termo de tempo de chamada).
+=======
+- A parameter is the variable listed inside the parentheses in the function declaration (it's a declaration time term).
+- An argument is the value that is passed to the function when it is called (it's a call time term).
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Declaramos funções listando seus parâmetros e as chamamos de passagem de argumentos.
@@ -205,7 +214,17 @@ function showMessage(from, *!*text = "nenhum texto fornecido"*/!*) {
showMessage("Ann"); // Ann: nenhum texto fornecido
```
+<<<<<<< HEAD
Agora se o parâmetro `text` não for passado, ele receberá o valor `"nenhum texto fornecido"`
+=======
+Now if the `text` parameter is not passed, it will get the value `"no text given"`.
+
+The default value also jumps in if the parameter exists, but strictly equals `undefined`, like this:
+
+```js
+showMessage("Ann", undefined); // Ann: no text given
+```
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Aqui `"nenhum texto fornecido"` é uma string, mas pode ser uma expressão mais complexa, que só é avaliada e atribuída se o parâmetro estiver ausente. Então, isso também é possível:
@@ -224,9 +243,47 @@ No exemplo acima, `anotherFunction()` não é chamado se o parâmetro `text` for
Por outro lado, é chamado independentemente toda vez que `text` está faltando.
```
+<<<<<<< HEAD
### Parâmetros padrão alternativos
Às vezes, faz sentido atribuir valores padrão para parâmetros não na declaração da função, mas em um estágio posterior.
+=======
+````smart header="Default parameters in old JavaScript code"
+Several years ago, JavaScript didn't support the syntax for default parameters. So people used other ways to specify them.
+
+Nowadays, we can come across them in old scripts.
+
+For example, an explicit check for `undefined`:
+
+```js
+function showMessage(from, text) {
+*!*
+ if (text === undefined) {
+ text = 'no text given';
+ }
+*/!*
+
+ alert( from + ": " + text );
+}
+```
+
+...Or using the `||` operator:
+
+```js
+function showMessage(from, text) {
+ // If the value of text is falsy, assign the default value
+ // this assumes that text == "" is the same as no text at all
+ text = text || 'no text given';
+ ...
+}
+```
+````
+
+
+### Alternative default parameters
+
+Sometimes it makes sense to assign default values for parameters at a later stage after the function declaration.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Podemos verificar se o parâmetro é passado durante a execução da função, comparando-o com `undefined`:
@@ -421,7 +478,11 @@ Esses exemplos assumem significados comuns de prefixos. Você e sua equipe são
```smart header="Nomes de função ultracurtos"
As funções que são usadas *com muita frequência* às vezes têm nomes ultracurtos.
+<<<<<<< HEAD
Por exemplo, o framework [jQuery](http://jquery.com) define uma função com `$`. A biblioteca [Lodash](http://lodash.com/) tem sua função central chamada `_`.
+=======
+For example, the [jQuery](https://jquery.com/) framework defines a function with `$`. The [Lodash](https://lodash.com/) library has its core function named `_`.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Estas são exceções. Geralmente, os nomes das funções devem ser concisos e descritivos.
```
@@ -489,7 +550,11 @@ function name(parameters, delimited, by, comma) {
Para tornar o código limpo e fácil de entender, é recomendável usar principalmente variáveis e parâmetros locais na função, não variáveis externas.
+<<<<<<< HEAD
É sempre mais fácil entender uma função que obtém parâmetros, trabalha com eles e retorna um resultado do que uma função que não obtém parâmetros, mas modifica variáveis externas como efeito colateral.
+=======
+It is always easier to understand a function which gets parameters, works with them and returns a result than a function which gets no parameters, but modifies outer variables as a side effect.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Nomenclatura da função:
diff --git a/1-js/02-first-steps/16-function-expressions/article.md b/1-js/02-first-steps/16-function-expressions/article.md
index b952d5943..c6dd891bd 100644
--- a/1-js/02-first-steps/16-function-expressions/article.md
+++ b/1-js/02-first-steps/16-function-expressions/article.md
@@ -82,7 +82,7 @@ let sayHi = function() { // (1) create
alert( "Hello" );
};
-let func = sayHi;
+let func = sayHi; //(2)
// ...
```
diff --git a/1-js/02-first-steps/17-arrow-functions-basics/article.md b/1-js/02-first-steps/17-arrow-functions-basics/article.md
index 3728b4898..2b209c4cd 100644
--- a/1-js/02-first-steps/17-arrow-functions-basics/article.md
+++ b/1-js/02-first-steps/17-arrow-functions-basics/article.md
@@ -48,7 +48,11 @@ Como pode ver, `(a, b) => a + b` significa uma função que aceita dois argument
alert( double(3) ); // 6
```
+<<<<<<< HEAD
- Se não houver argumentos, os parênteses irão estar vazios (mas devem estar presentes):
+=======
+- If there are no arguments, parentheses are empty, but they must be present:
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
```js run
let sayHi = () => alert("Olá!");
@@ -64,8 +68,13 @@ Por exemplo, para criar dinamicamente uma função:
let age = prompt("Que idade tem?", 18);
let welcome = (age < 18) ?
+<<<<<<< HEAD
() => alert('Olá') :
() => alert("Saudações!");
+=======
+ () => alert('Hello!') :
+ () => alert("Greetings!");
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
welcome();
```
@@ -76,9 +85,15 @@ Elas são muito convenientes para ações simples numa única-linha, quando esta
## Funções seta de múltiplas linhas
+<<<<<<< HEAD
Os exemplos acima tomaram os argumentos à esquerda de `=>` e avaliaram a expressão à direita com eles.
Por vezes, precisamos de algo um pouco mais complexo, como de múltiplas expressões ou instruções. Isso também é possível, mas devemos colocar elas dentro de chavetas. Depois, usamos um `return` normal com elas.
+=======
+The arrow functions that we've seen so far were very simple. They took arguments from the left of `=>`, evaluated and returned the right-side expression with them.
+
+Sometimes we need a more complex function, with multiple expressions and statements. In that case, we can enclose them in curly braces. The major difference is that curly braces require a `return` within them to return a value (just like a regular function does).
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
Desta forma:
@@ -105,7 +120,14 @@ Por ora, podemos já usar funções seta para ações numa única-linha e *callb
## Resumo
+<<<<<<< HEAD
Funções seta são práticas para ações numa única-linha. Elas vêm em dois sabores:
1. Sem chavetas: `(...args) => expression` -- o lado direito é uma expressão: a função a avalia e retorna o resultado.
2. Com chavetas: `(...args) => { body }` -- chavetas nos permitem escrever múltiplas instruções dentro da função, mas precisamos de um explícito `return` para retornar alguma coisa.
+=======
+Arrow functions are handy for simple actions, especially for one-liners. They come in two flavors:
+
+1. Without curly braces: `(...args) => expression` -- the right side is an expression: the function evaluates it and returns the result. Parentheses can be omitted, if there's only a single argument, e.g. `n => n*2`.
+2. With curly braces: `(...args) => { body }` -- brackets allow us to write multiple statements inside the function, but we need an explicit `return` to return something.
+>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b
diff --git a/1-js/02-first-steps/18-javascript-specials/article.md b/1-js/02-first-steps/18-javascript-specials/article.md
index 016214e3b..0ba505066 100644
--- a/1-js/02-first-steps/18-javascript-specials/article.md
+++ b/1-js/02-first-steps/18-javascript-specials/article.md
@@ -103,13 +103,13 @@ More in: (253-1) or be less than -(253-1), as we mentioned earlier in the chapter (253-1) or be less than -(253-1), as we mentioned earlier in the chapter + This functionality is supported in most modern browsers. After the actions are taken, the
alert will trigger immediately.
+
+## FinalizationRegistry
+
+Now it is time to talk about finalizers. Before we move on, let's clarify the terminology:
+
+**Cleanup callback (finalizer)** - is a function that is executed, when an object, registered in the `FinalizationRegistry`, is deleted from memory by the garbage collector.
+
+Its purpose - is to provide the ability to perform additional operations, related to the object, after it has been finally deleted from memory.
+
+**Registry** (or `FinalizationRegistry`) - is a special object in JavaScript that manages the registration and unregistration of objects and their cleanup callbacks.
+
+This mechanism allows registering an object to track and associate a cleanup callback with it.
+Essentially it is a structure that stores information about registered objects and their cleanup callbacks, and then automatically invokes those callbacks when the objects are deleted from memory.
+
+To create an instance of the `FinalizationRegistry`, it needs to call its constructor, which takes a single argument - the cleanup callback (finalizer).
+
+Syntax:
+
+```js
+function cleanupCallback(heldValue) {
+ // cleanup callback code
+}
+
+const registry = new FinalizationRegistry(cleanupCallback);
+```
+
+Here:
+
+- `cleanupCallback` - a cleanup callback that will be automatically called when a registered object is deleted from memory.
+- `heldValue` - the value that is passed as an argument to the cleanup callback. If `heldValue` is an object, the registry keeps a strong reference to it.
+- `registry` - an instance of `FinalizationRegistry`.
+
+`FinalizationRegistry` methods:
+
+- `register(target, heldValue [, unregisterToken])` - used to register objects in the registry.
+
+ `target` - the object being registered for tracking. If the `target` is garbage collected, the cleanup callback will be called with `heldValue` as its argument.
+
+ Optional `unregisterToken` – an unregistration token. It can be passed to unregister an object before the garbage collector deletes it. Typically, the `target` object is used as `unregisterToken`, which is the standard practice.
+- `unregister(unregisterToken)` - the `unregister` method is used to unregister an object from the registry. It takes one argument - `unregisterToken` (the unregister token that was obtained when registering the object).
+
+Now let's move on to a simple example. Let's use the already-known `user` object and create an instance of `FinalizationRegistry`:
+
+```js
+let user = { name: "John" };
+
+const registry = new FinalizationRegistry((heldValue) => {
+ console.log(`${heldValue} has been collected by the garbage collector.`);
+});
+```
+
+Then, we will register the object, that requires a cleanup callback by calling the `register` method:
+
+```js
+registry.register(user, user.name);
+```
+
+The registry does not keep a strong reference to the object being registered, as this would defeat its purpose. If the registry kept a strong reference, then the object would never be garbage collected.
+
+If the object is deleted by the garbage collector, our cleanup callback may be called at some point in the future, with the `heldValue` passed to it:
+
+```js
+// When the user object is deleted by the garbage collector, the following message will be printed in the console:
+"John has been collected by the garbage collector."
+```
+
+There are also situations where, even in implementations that use a cleanup callback, there is a chance that it will not be called.
+
+For example:
+- When the program fully terminates its operation (for example, when closing a tab in a browser).
+- When the `FinalizationRegistry` instance itself is no longer reachable to JavaScript code.
+ If the object that creates the `FinalizationRegistry` instance goes out of scope or is deleted, the cleanup callbacks registered in that registry might also not be invoked.
+
+## Caching with FinalizationRegistry
+
+Returning to our *weak* cache example, we can notice the following:
+- Even though the values wrapped in the `WeakRef` have been collected by the garbage collector, there is still an issue of "memory leakage" in the form of the remaining keys, whose values have been collected by the garbage collector.
+
+Here is an improved caching example using `FinalizationRegistry`:
+
+```js
+function fetchImg() {
+ // abstract function for downloading images...
+}
+
+function weakRefCache(fetchImg) {
+ const imgCache = new Map();
+
+ *!*
+ const registry = new FinalizationRegistry((imgName) => { // (1)
+ const cachedImg = imgCache.get(imgName);
+ if (cachedImg && !cachedImg.deref()) imgCache.delete(imgName);
+ });
+ */!*
+
+ return (imgName) => {
+ const cachedImg = imgCache.get(imgName);
+
+ if (cachedImg?.deref()) {
+ return cachedImg?.deref();
+ }
+
+ const newImg = fetchImg(imgName);
+ imgCache.set(imgName, new WeakRef(newImg));
+ *!*
+ registry.register(newImg, imgName); // (2)
+ */!*
+
+ return newImg;
+ };
+}
+
+const getCachedImg = weakRefCache(fetchImg);
+```
+
+1. To manage the cleanup of "dead" cache entries, when the associated `WeakRef` objects are collected by the garbage collector, we create a `FinalizationRegistry` cleanup registry.
+
+ The important point here is, that in the cleanup callback, it should be checked, if the entry was deleted by the garbage collector and not re-added, in order not to delete a "live" entry.
+2. Once the new value (image) is downloaded and put into the cache, we register it in the finalizer registry to track the `WeakRef` object.
+
+This implementation contains only actual or "live" key/value pairs.
+In this case, each `WeakRef` object is registered in the `FinalizationRegistry`.
+And after the objects are cleaned up by the garbage collector, the cleanup callback will delete all `undefined` values.
+
+Here is a visual representation of the updated code:
+
+
+
+A key aspect of the updated implementation is that finalizers allow parallel processes to be created between the "main" program and cleanup callbacks.
+In the context of JavaScript, the "main" program - is our JavaScript-code, that runs and executes in our application or web page.
+
+Hence, from the moment an object is marked for deletion by the garbage collector, and to the actual execution of the cleanup callback, there may be a certain time gap.
+It is important to understand that during this time gap, the main program can make any changes to the object or even bring it back to memory.
+
+That's why, in the cleanup callback, we must check to see if an entry has been added back to the cache by the main program to avoid deleting "live" entries.
+Similarly, when searching for a key in the cache, there is a chance that the value has been deleted by the garbage collector, but the cleanup callback has not been executed yet.
+
+Such situations require special attention if you are working with `FinalizationRegistry`.
+
+## Using WeakRef and FinalizationRegistry in practice
+
+Moving from theory to practice, imagine a real-life scenario, where a user synchronizes their photos on a mobile device with some cloud service
+(such as [iCloud](https://en.wikipedia.org/wiki/ICloud) or [Google Photos](https://en.wikipedia.org/wiki/Google_Photos)),
+and wants to view them from other devices. In addition to the basic functionality of viewing photos, such services offer a lot of additional features, for example:
+
+- Photo editing and video effects.
+- Creating "memories" and albums.
+- Video montage from a series of photos.
+- ...and much more.
+
+Here, as an example, we will use a fairly primitive implementation of such a service.
+The main point - is to show a possible scenario of using `WeakRef` and `FinalizationRegistry` together in real life.
+
+Here is what it looks like:
+
+
+
++On the left side, there is a cloud library of photos (they are displayed as thumbnails). +We can select the images we need and create a collage, by clicking the "Create collage" button on the right side of the page. +Then, the resulting collage can be downloaded as an image. +
+ +To increase page loading speed, it would be reasonable to download and display photo thumbnails in *compressed* quality. +But, to create a collage from selected photos, download and use them in *full-size* quality. + +Below, we can see, that the intrinsic size of the thumbnails is 240x240 pixels. +The size was chosen on purpose to increase loading speed. +Moreover, we do not need full-size photos in preview mode. + + + +
+Let's assume, that we need to create a collage of 4 photos: we select them, and then click the "Create collage" button. +At this stage, the already known to us
weakRefCache function checks whether the required image is in the cache.
+If not, it downloads it from the cloud and puts it in the cache for further use.
+This happens for each selected image:
++ + + + + +Paying attention to the output in the console, you can see, which of the photos were downloaded from the cloud - this is indicated by FETCHED_IMAGE. +Since this is the first attempt to create a collage, this means, that at this stage the "weak cache" was still empty, and all the photos were downloaded from the cloud and put in it. + +But, along with the process of downloading images, there is also a process of memory cleanup by the garbage collector. +This means, that the object stored in the cache, which we refer to, using a weak reference, is deleted by the garbage collector. +And our finalizer executes successfully, thereby deleting the key, by which the image was stored in the cache. +CLEANED_IMAGE notifies us about it: + + + +
+Next, we realize that we do not like the resulting collage, and decide to change one of the images and create a new one. +To do this, just deselect the unnecessary image, select another one, and click the "Create collage" button again: +
+ + + +
+But this time not all images were downloaded from the network, and one of them was taken from the weak cache: the CACHED_IMAGE message tells us about it. +This means that at the time of collage creation, the garbage collector had not yet deleted our image, and we boldly took it from the cache, +thereby reducing the number of network requests and speeding up the overall time of the collage creation process: +
+ + + +
+Let's "play around" a little more, by replacing one of the images again and creating a new collage: +
+ + + +
+This time the result is even more impressive. Of the 4 images selected, 3 of them were taken from the weak cache, and only one had to be downloaded from the network. +The reduction in network load was about 75%. Impressive, isn't it? +
+ + + + + +Of course, it is important to remember, that such behavior is not guaranteed, and depends on the specific implementation and operation of the garbage collector. + +Based on this, a completely logical question immediately arises: why do not we use an ordinary cache, where we can manage its entities ourselves, instead of relying on the garbage collector? +That's right, in the vast majority of cases there is no need to use `WeakRef` and `FinalizationRegistry`. + +Here, we simply demonstrated an alternative implementation of similar functionality, using a non-trivial approach with interesting language features. +Still, we cannot rely on this example, if we need a constant and predictable result. + +You can [open this example in the sandbox](sandbox:weakref-finalizationregistry). + +## Summary + +`WeakRef` - designed to create weak references to objects, allowing them to be deleted from memory by the garbage collector if there are no longer strong references to them. +This is beneficial for addressing excessive memory usage and optimizing the utilization of system resources in applications. + +`FinalizationRegistry` - is a tool for registering callbacks, that are executed when objects that are no longer strongly referenced, are destroyed. +This allows releasing resources associated with the object or performing other necessary operations before deleting the object from memory. \ No newline at end of file diff --git a/1-js/99-js-misc/07-weakref-finalizationregistry/google-chrome-developer-tools.png b/1-js/99-js-misc/07-weakref-finalizationregistry/google-chrome-developer-tools.png new file mode 100644 index 000000000..021637342 Binary files /dev/null and b/1-js/99-js-misc/07-weakref-finalizationregistry/google-chrome-developer-tools.png differ diff --git a/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-dom.view/index.css b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-dom.view/index.css new file mode 100644 index 000000000..f6df812d0 --- /dev/null +++ b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-dom.view/index.css @@ -0,0 +1,49 @@ +.app { + display: flex; + flex-direction: column; + gap: 16px; +} + +.start-messages { + width: fit-content; +} + +.window { + width: 100%; + border: 2px solid #464154; + overflow: hidden; +} + +.window__header { + position: sticky; + padding: 8px; + display: flex; + justify-content: space-between; + align-items: center; + background-color: #736e7e; +} + +.window__title { + margin: 0; + font-size: 24px; + font-weight: 700; + color: white; + letter-spacing: 1px; +} + +.window__button { + padding: 4px; + background: #4f495c; + outline: none; + border: 2px solid #464154; + color: white; + font-size: 16px; + cursor: pointer; +} + +.window__body { + height: 250px; + padding: 16px; + overflow: scroll; + background-color: #736e7e33; +} \ No newline at end of file diff --git a/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-dom.view/index.html b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-dom.view/index.html new file mode 100644 index 000000000..7f93af4c7 --- /dev/null +++ b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-dom.view/index.html @@ -0,0 +1,28 @@ + + + + + + +
+
+
+
+
+
+
+
diff --git a/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-dom.view/index.js b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-dom.view/index.js
new file mode 100644
index 000000000..ea55b4478
--- /dev/null
+++ b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-dom.view/index.js
@@ -0,0 +1,24 @@
+const startMessagesBtn = document.querySelector('.start-messages'); // (1)
+const closeWindowBtn = document.querySelector('.window__button'); // (2)
+const windowElementRef = new WeakRef(document.querySelector(".window__body")); // (3)
+
+startMessagesBtn.addEventListener('click', () => { // (4)
+ startMessages(windowElementRef);
+ startMessagesBtn.disabled = true;
+});
+
+closeWindowBtn.addEventListener('click', () => document.querySelector(".window__body").remove()); // (5)
+
+
+const startMessages = (element) => {
+ const timerId = setInterval(() => { // (6)
+ if (element.deref()) { // (7)
+ const payload = document.createElement("p");
+ payload.textContent = `Message: System status OK: ${new Date().toLocaleTimeString()}`;
+ element.deref().append(payload);
+ } else { // (8)
+ alert("The element has been deleted."); // (9)
+ clearInterval(timerId);
+ }
+ }, 1000);
+};
\ No newline at end of file
diff --git a/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-01.svg b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-01.svg
new file mode 100644
index 000000000..2a507dbcd
--- /dev/null
+++ b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-01.svg
@@ -0,0 +1,32 @@
+
+
\ No newline at end of file
diff --git a/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-02.svg b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-02.svg
new file mode 100644
index 000000000..6cc199a12
--- /dev/null
+++ b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-02.svg
@@ -0,0 +1,33 @@
+
+
\ No newline at end of file
diff --git a/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-03.svg b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-03.svg
new file mode 100644
index 000000000..949a14f9f
--- /dev/null
+++ b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-03.svg
@@ -0,0 +1,75 @@
+
+
\ No newline at end of file
diff --git a/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-04.svg b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-04.svg
new file mode 100644
index 000000000..1177d6580
--- /dev/null
+++ b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-04.svg
@@ -0,0 +1,77 @@
+
+
\ No newline at end of file
diff --git a/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-05.svg b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-05.svg
new file mode 100644
index 000000000..e738f8e7e
--- /dev/null
+++ b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry-05.svg
@@ -0,0 +1,103 @@
+
+
\ No newline at end of file
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diff --git a/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry.view/index.css b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry.view/index.css
new file mode 100644
index 000000000..e6c9e3960
--- /dev/null
+++ b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry.view/index.css
@@ -0,0 +1,285 @@
+:root {
+ --mineralGreen: 60, 98, 85;
+ --viridianGreen: 97, 135, 110;
+ --swampGreen: 166, 187, 141;
+ --fallGreen: 234, 231, 177;
+ --brinkPink: #FA7070;
+ --silverChalice: 178, 178, 178;
+ --white: 255, 255, 255;
+ --black: 0, 0, 0;
+
+ --topBarHeight: 64px;
+ --itemPadding: 32px;
+ --containerGap: 8px;
+}
+
+@keyframes zoom-in {
+ 0% {
+ transform: scale(1, 1);
+ }
+
+ 100% {
+ transform: scale(1.30, 1.30);
+ }
+}
+
+body, html {
+ margin: 0;
+ padding: 0;
+}
+
+.app {
+ min-height: 100vh;
+ background-color: rgba(var(--viridianGreen), 0.5);
+}
+
+.header {
+ height: var(--topBarHeight);
+ padding: 0 24px;
+ display: flex;
+ justify-content: space-between;
+ align-items: center;
+ background-color: rgba(var(--mineralGreen), 1);
+}
+
+.header-text {
+ color: white;
+}
+
+.container {
+ display: flex;
+ gap: 24px;
+ padding: var(--itemPadding);
+}
+
+.item {
+ width: 50%;
+}
+
+.item--scrollable {
+ overflow-y: scroll;
+ height: calc(100vh - var(--topBarHeight) - (var(--itemPadding) * 2));
+}
+
+.thumbnails-container {
+ display: flex;
+ flex-wrap: wrap;
+ gap: 8px;
+ justify-content: center;
+ align-items: center;
+}
+
+.thumbnail-item {
+ width: calc(25% - var(--containerGap));
+ cursor: pointer;
+ position: relative;
+}
+
+.thumbnail-item:hover {
+ z-index: 1;
+ animation: zoom-in 0.1s forwards;
+}
+
+.thumbnail-item--selected {
+ outline: 3px solid rgba(var(--fallGreen), 1);
+ outline-offset: -3px;
+}
+
+.badge {
+ width: 16px;
+ height: 16px;
+ display: flex;
+ justify-content: center;
+ align-items: center;
+ padding: 4px;
+ position: absolute;
+ right: 8px;
+ bottom: 8px;
+ border-radius: 50%;
+ border: 2px solid rgba(var(--fallGreen), 1);
+ background-color: rgba(var(--swampGreen), 1);
+}
+
+.check {
+ display: inline-block;
+ transform: rotate(45deg);
+ border-bottom: 2px solid white;
+ border-right: 2px solid white;
+ width: 6px;
+ height: 12px;
+}
+
+.img {
+ width: 100%;
+ height: 100%;
+ object-fit: cover;
+}
+
+.actions {
+ display: flex;
+ flex-wrap: wrap;
+ justify-content: center;
+ align-content: center;
+ padding: 0 0 16px 0;
+ gap: 8px;
+}
+
+.select {
+ padding: 16px;
+ cursor: pointer;
+ font-weight: 700;
+ color: rgba(var(--black), 1);
+ border: 2px solid rgba(var(--swampGreen), 0.5);
+ background-color: rgba(var(--swampGreen), 1);
+}
+
+.select:disabled {
+ cursor: not-allowed;
+ background-color: rgba(var(--silverChalice), 1);
+ color: rgba(var(--black), 0.5);
+ border: 2px solid rgba(var(--black), 0.25);
+}
+
+.btn {
+ outline: none;
+ padding: 16px;
+ cursor: pointer;
+ font-weight: 700;
+ color: rgba(var(--black), 1);
+ border: 2px solid rgba(var(--black), 0.5);
+}
+
+.btn--primary {
+ background-color: rgba(var(--mineralGreen), 1);
+}
+
+.btn--primary:hover:not([disabled]) {
+ background-color: rgba(var(--mineralGreen), 0.85);
+}
+
+.btn--secondary {
+ background-color: rgba(var(--viridianGreen), 0.5);
+}
+
+.btn--secondary:hover:not([disabled]) {
+ background-color: rgba(var(--swampGreen), 0.25);
+}
+
+.btn--success {
+ background-color: rgba(var(--fallGreen), 1);
+}
+
+.btn--success:hover:not([disabled]) {
+ background-color: rgba(var(--fallGreen), 0.85);
+}
+
+.btn:disabled {
+ cursor: not-allowed;
+ background-color: rgba(var(--silverChalice), 1);
+ color: rgba(var(--black), 0.5);
+ border: 2px solid rgba(var(--black), 0.25);
+}
+
+.previewContainer {
+ margin-bottom: 16px;
+ display: flex;
+ width: 100%;
+ height: 40vh;
+ overflow: scroll;
+ border: 3px solid rgba(var(--black), 1);
+}
+
+.previewContainer--disabled {
+ background-color: rgba(var(--black), 0.1);
+ cursor: not-allowed;
+}
+
+.canvas {
+ margin: auto;
+ display: none;
+}
+
+.canvas--ready {
+ display: block;
+}
+
+.spinnerContainer {
+ display: flex;
+ gap: 8px;
+ flex-direction: column;
+ align-content: center;
+ align-items: center;
+ margin: auto;
+}
+
+.spinnerContainer--hidden {
+ display: none;
+}
+
+.spinnerText {
+ margin: 0;
+ color: rgba(var(--mineralGreen), 1);
+}
+
+.spinner {
+ display: inline-block;
+ width: 50px;
+ height: 50px;
+ margin: auto;
+ border: 3px solid rgba(var(--mineralGreen), 0.3);
+ border-radius: 50%;
+ border-top-color: rgba(var(--mineralGreen), 0.9);
+ animation: spin 1s ease-in-out infinite;
+}
+
+@keyframes spin {
+ to {
+ transform: rotate(360deg);
+ }
+}
+
+.loggerContainer {
+ display: flex;
+ flex-direction: column;
+ gap: 8px;
+ padding: 0 8px 8px 8px;
+ width: 100%;
+ min-height: 30vh;
+ max-height: 30vh;
+ overflow: scroll;
+ border-left: 3px solid rgba(var(--black), 0.25);
+}
+
+.logger-title {
+ display: flex;
+ align-items: center;
+ padding: 8px;
+ position: sticky;
+ height: 40px;
+ min-height: 40px;
+ top: 0;
+ left: 0;
+ background-color: rgba(var(--viridianGreen), 1);
+ font-size: 24px;
+ font-weight: 700;
+ margin: 0;
+}
+
+.logger-item {
+ font-size: 14px;
+ padding: 8px;
+ border: 2px solid #5a5a5a;
+ color: white;
+}
+
+.logger--primary {
+ background-color: #13315a;
+}
+
+.logger--success {
+ background-color: #385a4e;
+}
+
+.logger--error {
+ background-color: #5a1a24;
+}
\ No newline at end of file
diff --git a/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry.view/index.html b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry.view/index.html
new file mode 100644
index 000000000..7ce52f927
--- /dev/null
+++ b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry.view/index.html
@@ -0,0 +1,49 @@
+
+
+
+
+
+
+
+
+
+
+ Messages:
+ +
+ No messages.
+
+
+
+
+
+
+
+
+
+
diff --git a/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry.view/index.js b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry.view/index.js
new file mode 100644
index 000000000..983b34d9a
--- /dev/null
+++ b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry.view/index.js
@@ -0,0 +1,228 @@
+import {
+ createImageFile,
+ loadImage,
+ weakRefCache,
+ LAYOUTS,
+ images,
+ THUMBNAIL_PARAMS,
+ stateObj,
+} from "./utils.js";
+
+export const state = new Proxy(stateObj, {
+ set(target, property, value) {
+ const previousValue = target[property];
+
+ target[property] = value;
+
+ if (previousValue !== value) {
+ handleStateChange(target);
+ }
+
+ return true;
+ },
+});
+
+// Elements.
+const thumbnailsContainerEl = document.querySelector(".thumbnails-container");
+const selectEl = document.querySelector(".select");
+const previewContainerEl = document.querySelector(".previewContainer");
+const canvasEl = document.querySelector(".canvas");
+const createCollageBtn = document.querySelector(".btn-create-collage");
+const startOverBtn = document.querySelector(".btn-start-over");
+const downloadBtn = document.querySelector(".btn-download");
+const spinnerContainerEl = document.querySelector(".spinnerContainer");
+const spinnerTextEl = document.querySelector(".spinnerText");
+const loggerContainerEl = document.querySelector(".loggerContainer");
+
+// Renders.
+// Render thumbnails previews.
+images.forEach((img) => {
+ const thumbnail = document.createElement("div");
+ thumbnail.classList.add("thumbnail-item");
+
+ thumbnail.innerHTML = `
+ + Photo Library Collage +
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Logger:
+Logger:
'; +}; + +const downloadCollage = () => { + const date = new Date(); + const fileName = `Collage-${date.getDay()}-${date.getMonth()}-${date.getFullYear()}.png`; + const img = canvasEl.toDataURL("image/png"); + const link = document.createElement("a"); + link.download = fileName; + link.href = img; + link.click(); + link.remove(); +}; + +const changeLayout = ({ target }) => { + state.currentLayout = JSON.parse(target.value); +}; + +// Listeners. +selectEl.addEventListener("change", changeLayout); +createCollageBtn.addEventListener("click", createCollage); +startOverBtn.addEventListener("click", startOver); +downloadBtn.addEventListener("click", downloadCollage); diff --git a/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry.view/utils.js b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry.view/utils.js new file mode 100644 index 000000000..f0140c116 --- /dev/null +++ b/1-js/99-js-misc/07-weakref-finalizationregistry/weakref-finalizationregistry.view/utils.js @@ -0,0 +1,321 @@ +const loggerContainerEl = document.querySelector(".loggerContainer"); + +export const images = [ + { + img: "https://images.unsplash.com/photo-1471357674240-e1a485acb3e1", + }, + { + img: "https://images.unsplash.com/photo-1589118949245-7d38baf380d6", + }, + { + img: "https://images.unsplash.com/photo-1527631746610-bca00a040d60", + }, + { + img: "https://images.unsplash.com/photo-1500835556837-99ac94a94552", + }, + { + img: "https://images.unsplash.com/photo-1503220317375-aaad61436b1b", + }, + { + img: "https://images.unsplash.com/photo-1501785888041-af3ef285b470", + }, + { + img: "https://images.unsplash.com/photo-1528543606781-2f6e6857f318", + }, + { + img: "https://images.unsplash.com/photo-1523906834658-6e24ef2386f9", + }, + { + img: "https://images.unsplash.com/photo-1539635278303-d4002c07eae3", + }, + { + img: "https://images.unsplash.com/photo-1533105079780-92b9be482077", + }, + { + img: "https://images.unsplash.com/photo-1516483638261-f4dbaf036963", + }, + { + img: "https://images.unsplash.com/photo-1502791451862-7bd8c1df43a7", + }, + { + img: "https://plus.unsplash.com/premium_photo-1663047367140-91adf819d007", + }, + { + img: "https://images.unsplash.com/photo-1506197603052-3cc9c3a201bd", + }, + { + img: "https://images.unsplash.com/photo-1517760444937-f6397edcbbcd", + }, + { + img: "https://images.unsplash.com/photo-1518684079-3c830dcef090", + }, + { + img: "https://images.unsplash.com/photo-1505832018823-50331d70d237", + }, + { + img: "https://images.unsplash.com/photo-1524850011238-e3d235c7d4c9", + }, + { + img: "https://plus.unsplash.com/premium_photo-1661277758451-b5053309eea1", + }, + { + img: "https://images.unsplash.com/photo-1541410965313-d53b3c16ef17", + }, + { + img: "https://images.unsplash.com/photo-1528702748617-c64d49f918af", + }, + { + img: "https://images.unsplash.com/photo-1502003148287-a82ef80a6abc", + }, + { + img: "https://plus.unsplash.com/premium_photo-1661281272544-5204ea3a481a", + }, + { + img: "https://images.unsplash.com/photo-1503457574462-bd27054394c1", + }, + { + img: "https://images.unsplash.com/photo-1499363536502-87642509e31b", + }, + { + img: "https://images.unsplash.com/photo-1551918120-9739cb430c6d", + }, + { + img: "https://plus.unsplash.com/premium_photo-1661382219642-43e54f7e81d7", + }, + { + img: "https://images.unsplash.com/photo-1497262693247-aa258f96c4f5", + }, + { + img: "https://images.unsplash.com/photo-1525254134158-4fd5fdd45793", + }, + { + img: "https://plus.unsplash.com/premium_photo-1661274025419-4c54107d5c48", + }, + { + img: "https://images.unsplash.com/photo-1553697388-94e804e2f0f6", + }, + { + img: "https://images.unsplash.com/photo-1574260031597-bcd9eb192b4f", + }, + { + img: "https://images.unsplash.com/photo-1536323760109-ca8c07450053", + }, + { + img: "https://images.unsplash.com/photo-1527824404775-dce343118ebc", + }, + { + img: "https://images.unsplash.com/photo-1612278675615-7b093b07772d", + }, + { + img: "https://images.unsplash.com/photo-1522010675502-c7b3888985f6", + }, + { + img: "https://images.unsplash.com/photo-1501555088652-021faa106b9b", + }, + { + img: "https://plus.unsplash.com/premium_photo-1669223469435-27e091439169", + }, + { + img: "https://images.unsplash.com/photo-1506012787146-f92b2d7d6d96", + }, + { + img: "https://images.unsplash.com/photo-1511739001486-6bfe10ce785f", + }, + { + img: "https://images.unsplash.com/photo-1553342385-111fd6bc6ab3", + }, + { + img: "https://images.unsplash.com/photo-1516546453174-5e1098a4b4af", + }, + { + img: "https://images.unsplash.com/photo-1527142879-95b61a0b8226", + }, + { + img: "https://images.unsplash.com/photo-1520466809213-7b9a56adcd45", + }, + { + img: "https://images.unsplash.com/photo-1516939884455-1445c8652f83", + }, + { + img: "https://images.unsplash.com/photo-1545389336-cf090694435e", + }, + { + img: "https://plus.unsplash.com/premium_photo-1669223469455-b7b734c838f4", + }, + { + img: "https://images.unsplash.com/photo-1454391304352-2bf4678b1a7a", + }, + { + img: "https://images.unsplash.com/photo-1433838552652-f9a46b332c40", + }, + { + img: "https://images.unsplash.com/photo-1506125840744-167167210587", + }, + { + img: "https://images.unsplash.com/photo-1522199873717-bc67b1a5e32b", + }, + { + img: "https://images.unsplash.com/photo-1495904786722-d2b5a19a8535", + }, + { + img: "https://images.unsplash.com/photo-1614094082869-cd4e4b2905c7", + }, + { + img: "https://images.unsplash.com/photo-1474755032398-4b0ed3b2ae5c", + }, + { + img: "https://images.unsplash.com/photo-1501554728187-ce583db33af7", + }, + { + img: "https://images.unsplash.com/photo-1515859005217-8a1f08870f59", + }, + { + img: "https://images.unsplash.com/photo-1531141445733-14c2eb7d4c1f", + }, + { + img: "https://images.unsplash.com/photo-1500259783852-0ca9ce8a64dc", + }, + { + img: "https://images.unsplash.com/photo-1510662145379-13537db782dc", + }, + { + img: "https://images.unsplash.com/photo-1573790387438-4da905039392", + }, + { + img: "https://images.unsplash.com/photo-1512757776214-26d36777b513", + }, + { + img: "https://images.unsplash.com/photo-1518855706573-84de4022b69b", + }, + { + img: "https://images.unsplash.com/photo-1500049242364-5f500807cdd7", + }, + { + img: "https://images.unsplash.com/photo-1528759335187-3b683174c86a", + }, +]; +export const THUMBNAIL_PARAMS = "w=240&h=240&fit=crop&auto=format"; + +// Console styles. +export const CONSOLE_BASE_STYLES = [ + "font-size: 12px", + "padding: 4px", + "border: 2px solid #5a5a5a", + "color: white", +].join(";"); +export const CONSOLE_PRIMARY = [ + CONSOLE_BASE_STYLES, + "background-color: #13315a", +].join(";"); +export const CONSOLE_SUCCESS = [ + CONSOLE_BASE_STYLES, + "background-color: #385a4e", +].join(";"); +export const CONSOLE_ERROR = [ + CONSOLE_BASE_STYLES, + "background-color: #5a1a24", +].join(";"); + +// Layouts. +export const LAYOUT_4_COLUMNS = { + name: "Layout 4 columns", + columns: 4, + itemWidth: 240, + itemHeight: 240, +}; +export const LAYOUT_8_COLUMNS = { + name: "Layout 8 columns", + columns: 8, + itemWidth: 240, + itemHeight: 240, +}; +export const LAYOUTS = [LAYOUT_4_COLUMNS, LAYOUT_8_COLUMNS]; + +export const createImageFile = async (src) => + new Promise((resolve, reject) => { + const img = new Image(); + img.src = src; + img.onload = () => resolve(img); + img.onerror = () => reject(new Error("Failed to construct image.")); + }); + +export const loadImage = async (url) => { + try { + const response = await fetch(url); + if (!response.ok) { + throw new Error(String(response.status)); + } + + return await response.blob(); + } catch (e) { + console.log(`%cFETCHED_FAILED: ${e}`, CONSOLE_ERROR); + } +}; + +export const weakRefCache = (fetchImg) => { + const imgCache = new Map(); + const registry = new FinalizationRegistry(({ imgName, size, type }) => { + const cachedImg = imgCache.get(imgName); + if (cachedImg && !cachedImg.deref()) { + imgCache.delete(imgName); + console.log( + `%cCLEANED_IMAGE: Url: ${imgName}, Size: ${size}, Type: ${type}`, + CONSOLE_ERROR, + ); + + const logEl = document.createElement("div"); + logEl.classList.add("logger-item", "logger--error"); + logEl.innerHTML = `CLEANED_IMAGE: Url: ${imgName}, Size: ${size}, Type: ${type}`; + loggerContainerEl.appendChild(logEl); + loggerContainerEl.scrollTop = loggerContainerEl.scrollHeight; + } + }); + + return async (imgName) => { + const cachedImg = imgCache.get(imgName); + + if (cachedImg?.deref() !== undefined) { + console.log( + `%cCACHED_IMAGE: Url: ${imgName}, Size: ${cachedImg.size}, Type: ${cachedImg.type}`, + CONSOLE_SUCCESS, + ); + + const logEl = document.createElement("div"); + logEl.classList.add("logger-item", "logger--success"); + logEl.innerHTML = `CACHED_IMAGE: Url: ${imgName}, Size: ${cachedImg.size}, Type: ${cachedImg.type}`; + loggerContainerEl.appendChild(logEl); + loggerContainerEl.scrollTop = loggerContainerEl.scrollHeight; + + return cachedImg?.deref(); + } + + const newImg = await fetchImg(imgName); + console.log( + `%cFETCHED_IMAGE: Url: ${imgName}, Size: ${newImg.size}, Type: ${newImg.type}`, + CONSOLE_PRIMARY, + ); + + const logEl = document.createElement("div"); + logEl.classList.add("logger-item", "logger--primary"); + logEl.innerHTML = `FETCHED_IMAGE: Url: ${imgName}, Size: ${newImg.size}, Type: ${newImg.type}`; + loggerContainerEl.appendChild(logEl); + loggerContainerEl.scrollTop = loggerContainerEl.scrollHeight; + + imgCache.set(imgName, new WeakRef(newImg)); + registry.register(newImg, { + imgName, + size: newImg.size, + type: newImg.type, + }); + + return newImg; + }; +}; + +export const stateObj = { + loading: false, + drawing: true, + collageRendered: false, + currentLayout: LAYOUTS[0], + selectedImages: new Set(), +}; diff --git a/2-ui/1-document/04-searching-elements-dom/article.md b/2-ui/1-document/04-searching-elements-dom/article.md index 8afed40ac..c92677344 100644 --- a/2-ui/1-document/04-searching-elements-dom/article.md +++ b/2-ui/1-document/04-searching-elements-dom/article.md @@ -52,8 +52,13 @@ Além disso, existe uma variável global nomeada por `id` que referencia o eleme ``` +<<<<<<< HEAD ```warn header="Por favor, não use variáveis globais nomeadas com id para acessar elementos" Esse comportamento é descrito [na especificação](https://html.spec.whatwg.org/multipage/window-object.html#named-access-on-the-window-object), mas é suportado principalmente por questões de compatibilidade. +======= +```warn header="Please don't use id-named global variables to access elements" +This behavior is described [in the specification](https://html.spec.whatwg.org/multipage/window-object.html#named-access-on-the-window-object), but it is supported mainly for compatibility. +>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b O navegador tenta nos ajudar misturando os namespaces do JavaScript e do DOM. Isso é bom para scripts simples, inseridos diretamente no HTML, mas geralmente não é algo bom. Pode haver conflitos de nomes. Além disso, quando alguém lê o código JavaScript e não tem o HTML à vista, não é óbvio de onde a variável vem. @@ -112,7 +117,11 @@ Em outras palavras, o resultado é o mesmo que `elem.querySelectorAll(css)[0]`, Os métodos anteriores estavam procurando no DOM. +<<<<<<< HEAD O método [elem.matches(css)](https://dom.spec.whatwg.org/#dom-element-matches) não procura por nada, apenas verifica se `elem` corresponde ao seletor CSS fornecido. Ele retorna `true` ou `false`. +======= +The [elem.matches(css)](https://dom.spec.whatwg.org/#dom-element-matches) does not look for anything, it merely checks if `elem` matches the given CSS-selector. It returns `true` or `false`. +>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b O método é útil quando estamos iterando sobre elementos (como em um array ou algo do tipo) e tentando filtrar aqueles que nos interessam. @@ -149,8 +158,13 @@ Poe exemplo:-
+<<<<<<< HEAD
- Capítulo 1
- Capítulo 2 +======= +
- Chapter 1 +
- Chapter 2 +>>>>>>> 540d753e90789205fc6e75c502f68382c87dea9b