Type Conversions (#16)

* Type Conversions

* miss one word

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

@@ -16,9 +16,10 @@ null + 1 = 1 // (5)
 undefined + 1 = NaN // (6)
 ```
 
-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.
+1. 字串的加法 `"" + 1` 會轉換 `1` 為字串：`"" + 1 = "1"`，然後得到 `"1" + 0` 再利用一樣的規則。
+2. 減法 `-` (就像多數數學運算) 只能用在數值上，它將空字串 `""` 轉成 `0`。
+3. 字串的加法會將數值 `5` 視為字串接在其後。
+4. 減法總是會轉換至數值，所以把 `"  -9  "` 變成數值 `-9` (忽略環繞的空白)。
+5. `null` 經由數值轉換變成 `0`。
+6. `undefined` 經由數值轉換變成 `NaN`。
+

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

@@ -2,9 +2,9 @@ importance: 5
 
 ---
 
-# Type conversions
+# 類型轉換
 
-What are results of these expressions?
+這些表達式的結果會是什麼？
 
 ```js no-beautify
 "" + 1 + 0
@@ -23,4 +23,5 @@ null + 1
 undefined + 1
 ```
 
-Think well, write down and then compare with the answer.
+好好想一下，把結果寫下來並和答案對照看看。
+

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

@@ -1,111 +1,111 @@
-# Type Conversions
+# 類型轉換
 
-Most of the time, operators and functions automatically convert the values given to them to the right type. 
+大多時候，運算子和函式會自動轉換給予它們的值為正確類型。
 
-For example, `alert` automatically converts any value to a string to show it. Mathematical operations convert values to numbers.
+例如，`alert` 自動將任何值轉換成字串並顯示，數學運算子會把值轉換成數值。
 
-There are also cases when we need to explicitly convert a value to the expected type.
+當然某些情況我們得明確地轉換一個值至預期的類型。
 
-```smart header="Not talking about objects yet"
-In this chapter, we won't cover objects. Instead, we'll study primitives first. Later, after we learn about objects, we'll see how object conversion works in the chapter <info:object-toprimitive>.
+```smart header="還沒開始談到物件類型"
+在這章節，我們將不會轉換物件類型，我們會從原生類型開始說起。等晚點我們學完物件後，會在章節 <info:object-toprimitive> 中談到物件是如何被轉換的。
 ```
 
 ## ToString
 
-String conversion happens when we need the string form of a value.
+字串轉換發生在我們需要得到某個值的字串型態時。
 
-For example, `alert(value)` does it to show the value.
+例如，`alert(value)` 就做這件事並顯示其值。
 
-We can also call the `String(value)` function to convert a value to a string:
+我們也可以呼叫 `String(value)` 函式把一個值轉為字串：
 
 ```js run
 let value = true;
 alert(typeof value); // boolean
 
 *!*
-value = String(value); // now value is a string "true"
+value = String(value); // 現在 value 是一個 "true" 字串
 alert(typeof value); // string
 */!*
 ```
 
-String conversion is mostly obvious. A `false` becomes `"false"`, `null` becomes `"null"`, etc.
+字串轉換通常很直觀，一個 `false` 變成 `"false"`，`null` 變成 `"null"` 等。
 
 ## ToNumber
 
-Numeric conversion happens in mathematical functions and expressions automatically.
+數值轉換自動發生在數學運算函式和表達式。
 
-For example, when division `/` is applied to non-numbers:
+例如，當除法 `/` 被運用在非數值上時：
 
 ```js run
-alert( "6" / "2" ); // 3, strings are converted to numbers
+alert( "6" / "2" ); // 3，字串被轉成數值
 ```
 
-We can use the `Number(value)` function to explicitly convert a `value` to a number:
+我們可以使用 `Number(value)` 函式來明確地轉換一個 `value` 為一個數值：
 
 ```js run
 let str = "123";
 alert(typeof str); // string
 
-let num = Number(str); // becomes a number 123
+let num = Number(str); // 變成數值 123
 
 alert(typeof num); // number
 ```
 
-Explicit conversion is usually required when we read a value from a string-based source like a text form but expect a number to be entered.
+這種明確轉換通常用在，當我們從一個類似文字基底的來源讀取一個值，但預期它要被作為一個數值讀入時。
 
-If the string is not a valid number, the result of such a conversion is `NaN`. For instance:
+如果該字串不是個有效的數值，轉換的結果會是 `NaN`，如：
 
 ```js run
-let age = Number("an arbitrary string instead of a number");
+let age = Number("任何非數字的字串");
 
-alert(age); // NaN, conversion failed
+alert(age); // NaN，轉換失敗
 ```
 
-Numeric conversion rules:
+數值轉換規則：
 
-| Value |  Becomes... |
+| 值 | 會變成... |
 |-------|-------------|
 |`undefined`|`NaN`|
 |`null`|`0`|
-|<code>true&nbsp;and&nbsp;false</code> | `1` and `0` |
-| `string` | Whitespaces 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`. |
+|<code>true&nbsp;和&nbsp;false</code> | `1` 和 `0` |
+| `string` | 先去除頭尾空白，如果剩下的字串是空字串則結果是 `0`，否則數值將被從剩下的字串中被 "讀取"，此時若有錯誤將產生 `NaN`。 |
 
-Examples:
+例子：
 
 ```js run
 alert( Number("   123   ") ); // 123
-alert( Number("123z") );      // NaN (error reading a number at "z")
+alert( Number("123z") );      // NaN (在 "z" 讀取數值時產生錯誤)
 alert( Number(true) );        // 1
 alert( Number(false) );       // 0
 ```
 
-Please note that `null` and `undefined` behave differently here: `null` becomes zero while `undefined` becomes `NaN`.
+請注意 `null` 和 `undefined` 的行為在此處不同：`null` 會變成零，而 `undefined` 會變成 `NaN`。
 
-````smart header="Addition '+' concatenates strings"
-Almost all mathematical operations convert values to numbers. A notable exception is addition `+`. If one of the added values is a string, the other one is also converted to a string.
+````smart header="加法 '+' 連接字串們"
+幾乎所有數學運算子都會將值轉成數值，而加法 `+` 是個值得一提的例外。如果加法某側運算元是個字串，另一側將也會被轉換成字串。
 
-Then, it concatenates (joins) them:
+然後兩者將被連接：
 
 ```js run
-alert( 1 + '2' ); // '12' (string to the right)
-alert( '1' + 2 ); // '12' (string to the left)
+alert( 1 + '2' ); // '12' (右側為字串)
+alert( '1' + 2 ); // '12' (左側為字串)
 ```
 
-This only happens when at least one of the arguments is a string. Otherwise, values are converted to numbers.
+這只發生在當至少一側的引數是字串時，否則值都會被轉為數值。
 ````
 
 ## ToBoolean
 
-Boolean conversion is the simplest one.
+布林轉換是最簡單的一個。
 
-It happens in logical operations (later we'll meet condition tests and other similar things) but can also be performed explicitly with a call to `Boolean(value)`.
+它發生在邏輯運算 (晚點我們將看到條件判斷和其它類似的東西)，但也可以經由呼叫 `Boolean(value)` 來明確地轉換。
 
-The conversion rule:
+轉換規則是：
 
-- Values that are intuitively "empty", like `0`, an empty string, `null`, `undefined`, and `NaN`, become `false`.
-- Other values become `true`.
+- 直觀上是 "空白" 的值，像是 `0`、空字串、`null`、`undefined` 和 `NaN`，都會變成 `false`。
+- 其他值變成 `true`。
 
-For instance:
+例如：
 
 ```js run
 alert( Boolean(1) ); // true
@@ -115,46 +115,45 @@ alert( Boolean("hello") ); // true
 alert( Boolean("") ); // false
 ```
 
-````warn header="Please note: the string with zero `\"0\"` is `true`"
-Some languages (namely PHP) treat `"0"` as `false`. But in JavaScript, a non-empty string is always `true`.
+````warn header="請注意：包含零的字串 `\"0\"` 將會是 `true`"
+某些語言 (如 PHP) 視 `"0"` 為 `false`，但在 JavaScript 中，一個非空字串都會是 `true`。
 
 ```js run
 alert( Boolean("0") ); // true
-alert( Boolean(" ") ); // spaces, also true (any non-empty string is true)
+alert( Boolean(" ") ); // 空白，也是 true (任何非空字串都是 true)
 ```
 ````
 
+## 總結
 
-## Summary
+三種最為廣泛使用的類型轉換是：轉字串、轉數值和轉布林。
 
-The three most widely used type conversions are to string, to number, and to boolean.
+**`ToString`** － 用於當我們輸出某些東西時，可使用 `String(value)` 來轉換，原生值的字串的轉換通常是很直觀的。
 
-**`ToString`** -- Occurs when we output something. Can be performed with `String(value)`. The conversion to string is usually obvious for primitive values.
+**`ToNumber`** － 用於數學運算，可使用 `Number(value)` 來轉換。
 
-**`ToNumber`** -- Occurs in math operations. Can be performed with `Number(value)`.
+按照以下規則轉換：
 
-The conversion follows the rules:
-
-| Value |  Becomes... |
+| 值 | 會變成... |
 |-------|-------------|
 |`undefined`|`NaN`|
 |`null`|`0`|
 |<code>true&nbsp;/&nbsp;false</code> | `1 / 0` |
-| `string` | The string is read "as is", whitespaces from both sides are ignored. An empty string becomes `0`. An error gives `NaN`. |
+| `string` | 字串 "依原樣" 讀取並忽略頭尾空白，若為空字串則為 `0`，有錯誤則成為 `NaN`。 |
 
-**`ToBoolean`** -- Occurs in logical operations. Can be performed with `Boolean(value)`.
+**`ToBoolean`** － 用於邏輯運算，可使用 `Boolean(value)` 來轉換。
 
-Follows the rules:
+規則是：
 
-| Value |  Becomes... |
+| 值 | 會變成... |
 |-------|-------------|
 |`0`, `null`, `undefined`, `NaN`, `""` |`false`|
-|any other value| `true` |
+|其它值| `true` |
 
+這些規則大多容易理解記憶，值得一提的是，大家常常在這些地方犯錯：
 
-Most of these rules are easy to understand and memorize. The notable exceptions where people usually make mistakes are:
+- `undefined` 轉成數值是 `NaN` 而非 `0`。
+- `"0"` 和像是 `"   "` 這種只包含空白的字串在轉成布林時是 true。
 
-- `undefined` is `NaN` as a number, not `0`.
-- `"0"` and space-only strings like `"   "` are true as a boolean.
+在此沒提到物件的轉換，我們將會晚點在專門介紹物件的章節 <info:object-toprimitive> 中提及，先讓我們了解更多 JavaScript 中基礎的內容。
 
-Objects aren't covered here. We'll return to them later in the chapter <info:object-toprimitive> that is devoted exclusively to objects after we learn more basic things about JavaScript.