finished function/ scope.md

Author: howardchi

doc/zh-TW/function/scopes.md

@@ -10,18 +10,13 @@
         console.log(i); // 10
     }
 
-> **Note:** When not used in an assignment, return statement or as a function 
-> argument, the `{...}` notation will get interpreted as a block statement and 
-> **not** as an object literal. This, in conjunction with 
-> [automatic insertion of semicolons](#core.semicolon), can lead to subtle errors.
+> **注意:** 如果不是在賦值語句中，而是在 return 表達式或者函數參數中， `{...}` 將會作為程式碼中的解析，而不是作為物件的字面語法解析。
+> 如果考慮到 [自動分號插入](#core.semicolon)，可能會造成一些不易察覺的錯誤。
 
+JavaScript 中沒有寫示的命名空間定義，這代表著它所有定義的東西都是 *全域共享* 在同一個命名空間下。
 
-There are also no distinct namespaces in JavaScript, which means that everything 
-gets defined in one *globally shared* namespace.
-
-Each time a variable is referenced, JavaScript will traverse upwards through all 
-the scopes until it finds it. In the case that it reaches the global scope and 
-still has not found the requested name, it will raise a `ReferenceError`.
+每次引用一個變數，JavaScript 會向上找整個作用域直到找到這個變數為止。
+如果在全域中無法找到那個變數，它會拋出 `ReferenceError` 錯誤碼。
 
 ### 全域變數的壞處
 
@@ -31,17 +26,14 @@ still has not found the requested name, it will raise a `ReferenceError`.
     // script B
     var foo = '42'
 
-The above two scripts do **not** have the same effect. Script A defines a 
-variable called `foo` in the *global* scope, and script B defines a `foo` in the
-*current* scope.
+上面兩個腳本 *不會* 有同樣的效果。腳本 A 在 *全域* 空間定義了變數 `foo`，腳本 B 定義了 `foo` 在目前的區間內。
 
-Again, that is **not** at all the *same effect*: not using `var` can have major 
-implications.
+再次強調，上面的效果是 **完全不同**，不使用 `var` 會導致隱性的全域變數。
 
-    // global scope
+    // 全域作用區
     var foo = 42;
     function test() {
-        // local scope
+        // 局部作用區
         foo = 21;
     }
     test();
@@ -51,52 +43,51 @@ Leaving out the `var` statement inside the function `test` will override the
 value of `foo`. While this might not seem like a big deal at first, having 
 thousands of lines of JavaScript and not using `var` will introduce horrible,
 hard-to-track-down bugs.
+在函數 `test` 中部使用 `var` 會覆蓋到原本在外面的 `foo`。
+雖然看起來不是什麼大問題，但是當程式有幾千行的時候沒有使用 `var` 會照成難以追蹤的臭蟲。
+
 
-    // global scope
+    // 全域作用域
     var items = [/* some list */];
     for(var i = 0; i < 10; i++) {
         subLoop();
     }
 
     function subLoop() {
-        // scope of subLoop
-        for(i = 0; i < 10; i++) { // missing var statement
-            // do amazing stuff!
+        // subLoop 的作用域
+        for(i = 0; i < 10; i++) { // 缺少了 var
+            // 做一些事情
         }
     }
 
-The outer loop will terminate after the first call to `subLoop`,  since `subLoop`
-overwrites the global value of `i`. Using a `var` for the second `for` loop would
-have easily avoided this error. The `var` statement should **never** be left out 
-unless the *desired effect* is to affect the outer scope.
+在外面的迴圈在呼叫第一次 `subLoop` 之後就會停止，因為 `subLoop` 全域變數中的 `i` 被覆蓋了。
+在第二次使用 `for` 迴圈的時候，使用 `var` 就可以避免這種錯誤。
+在宣告變數的時候 **絕對不要** 忘記 `var`，除非就是 `希望他的效果` 是取改變外部的作用域。
 
-### Local Variables
+### 局部變數
 
-The only source for local variables in JavaScript are
-[function](#function.general) parameters and variables declared via the 
-`var` statement.
+在 javascript 中能用兩種方式來宣告局部變數。
+[函式](#function.general) 參數和透過 `var` 來宣告變數。
 
-    // global scope
+    // 全域變數
     var foo = 1;
     var bar = 2;
     var i = 2;
 
     function test(i) {
-        // local scope of the function test
+        // 函式 test 內部的局部作用域
         i = 5;
 
         var foo = 3;
         bar = 4;
     }
     test(10);
 
-While `foo` and `i` are local variables inside the scope of the function `test`,
-the assignment of `bar` will override the global variable with the same name.
+`foo` 和 `i` 是它的局部變數在 `test` 函式中，但是在 `bar` 的賦值會覆蓋全區域的作用域內的同名變數。
 
-### Hoisting
+### 變數宣告
 
-JavaScript **hoists** declarations. This means that both `var` statements and
-`function` declarations will be moved to the top of their enclosing scope.
+JavaScript 會 **提昇** 變數宣告， 這代表著 `var` 和 `function` 的圈告都會被提升到當前作用域的頂端。
 
     bar();
     var bar = function() {};
@@ -115,16 +106,14 @@ JavaScript **hoists** declarations. This means that both `var` statements and
         }
     }
 
-The above code gets transformed before execution starts. JavaScript moves
-the `var` statements, as well as `function` declarations, to the top of the 
-nearest surrounding scope.
+在上面的程式碼會被轉化在執行之前。 JavaScript 會把 `var`，和 `function` 宣告，放到最頂端最接近的作用區間
 
-    // var statements got moved here
-    var bar, someValue; // default to 'undefined'
+    // var 被移到這裡
+    var bar, someValue; //  值等於 'undefined'
 
-    // the function declaration got moved up too
+    // function 的宣告也被搬上來
     function test(data) {
-        var goo, i, e; // missing block scope moves these here
+        var goo, i, e; // 沒有作用域的也被搬至頂端
         if (false) {
             goo = 1;
 
@@ -136,98 +125,79 @@ nearest surrounding scope.
         }
     }
 
-    bar(); // fails with a TypeError since bar is still 'undefined'
-    someValue = 42; // assignments are not affected by hoisting
+    bar(); // 出錯：TypeError ， bar 還是 'undefined'
+    someValue = 42; // 賦值語句不會被提昇規則影響
     bar = function() {};
 
     test();
 
-Missing block scoping will not only move `var` statements out of loops and
-their bodies, it will also make the results of certain `if` constructs 
-non-intuitive.
+沒有作用域區間不只會把 `var` 放到迴圈之外，還會使得 `if` 表達式更難看懂。
 
-In the original code, although the `if` statement seemed to modify the *global 
-variable* `goo`, it actually modifies the *local variable* - after hoisting 
-has been applied.
+在一般的程式中，雖然 `if` 表達式中看起來修改了 *全域變數* `goo`，但實際上在提昇規則被運用後，卻是在修改 *局部變數*
 
-Without knowledge of *hoisting*, one might suspect the code below would raise a
-`ReferenceError`.
+如果沒有提昇規則的話，可能會出現像下面的看起來會出現 `ReferenceError` 的錯誤。
 
-    // check whether SomeImportantThing has been initialized
+    // 檢查 SomeImportantThing 是否已經被初始化
     if (!SomeImportantThing) {
         var SomeImportantThing = {};
     }
 
-But of course, this works due to the fact that the `var` statement is being 
-moved to the top of the *global scope*.
+但是它沒有錯誤，因為 `var` 的表達式會被提升到 *全域作用域* 的頂端。
 
     var SomeImportantThing;
 
-    // other code might initialize SomeImportantThing here, or not
+    // 有些程式，可能會初始化。
+    SomeImportantThing here, or not
 
-    // make sure it's there
+    // 檢查是否已經被初始化。
     if (!SomeImportantThing) {
         SomeImportantThing = {};
     }
 
-### Name Resolution Order
-
-All scopes in JavaScript, including the *global scope*, have the special name 
-[`this`](#function.this), defined in them, which refers to the *current object*. 
+### 名稱解析順序
+ 
+JavaScript 中所有的作用區，包括 *全域作用域*，都有一個特殊的名字 [`this`](#function.this), 在它們裡面被定義，指向當前的物件
 
-Function scopes also have the name [`arguments`](#function.arguments), defined in
-them, which contains the arguments that were passed to the function.
+函式作用域也有一個名稱叫做 [`arguments`](#function.arguments), 定義它們，其中包括傳到函式內的參數。
 
-For example, when trying to access a variable named `foo` inside the scope of a 
-function, JavaScript will look up the name in the following order:
+例如，它們開始試著進入到 `foo` 的作用域裡面， JavaScript 會依照下面的順序去查詢：
 
- 1. In case there is a `var foo` statement in the current scope, use that.
- 2. If one of the function parameters is named `foo`, use that.
- 3. If the function itself is called `foo`, use that.
- 4. Go to the next outer scope, and start with **#1** again.
+ 1. 當作用域內是否有 `var foo` 的定義。
+ 2. 函式形式參數是否有使用 `foo` 名稱定義。
+ 3. 函式自身是剖叫做 `foo`。
+ 4. 回溯到上一個層級然後再從第一個開始往下去查。
 
-> **Note:** Having a parameter called `arguments` will **prevent** the creation 
-> of the default `arguments` object.
+> **注意: ** 自定義 `arguments` 參數會阻止原生的 `arguments` 的物件創立
 
-### Namespaces
+### 命名空間
 
-A common problem associated with having only one global namespace is the
-likelihood of running into problems where variable names clash. In JavaScript,
-this problem can easily be avoided with the help of *anonymous wrappers*.
+只有一個全域作用域會導致常見的錯誤是命名衝突。在 JavaScript 中可以透過 *匿名包裝器* 來解決。
 
     (function() {
-        // a self contained "namespace"
+        // 自己本身的匿名空間
         
         window.foo = function() {
-            // an exposed closure
+            // 對外公開的函式
         };
 
-    })(); // execute the function immediately
+    })(); // 馬上執行這個匿名函式
 
+匿名函式被認為是 [表達式](#function.general)因此為了要可以調用，它們會先被執行。
 
-Unnamed functions are considered [expressions](#function.general); so in order to
-being callable, they must first be evaluated.
-
-    ( // evaluate the function inside the parentheses
+    ( // 小括號內的先被執行
     function() {}
-    ) // and return the function object
-    () // call the result of the evaluation
+    ) // 回傳函數對象
+    () // 調用上面的執行結果
 
-There are other ways to evaluate and directly call the function expression
-which, while different in syntax, behave the same way.
+還有其他方式也可以像上面一樣調用函式的方式達到
 
-    // A few other styles for directly invoking the 
     !function(){}()
     +function(){}()
     (function(){}());
     // and so on...
 
 ### 結語
 
-It is recommended to always use an *anonymous wrapper* to encapsulate code in 
-its own namespace. This does not only protect code against name clashes, but it 
-also allows for better modularization of programs.
-
-Additionally, the use of global variables is considered **bad practice**. **Any**
-use of them indicates badly written code that is prone to errors and hard to maintain.
+建議最好是都用 *匿名包裝器* 來封裝你的程式碼在自己的命名區間內。這不僅是要防止命名衝突也可以使得程序更有模組化。
 
+另外，全域變數是個 **不好的** 習慣，因為它會帶來錯誤和更難去維護。