March 2012
Intermediate to advanced
244 pages
4h 42m
Chinese
Content preview from JavaScript 設計模式
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對 JavaScript 程式員來說，精通函式是重要的基本技能，因為函式在這個語言有許多用
途，它們可以執行多種任務；而其他語言可能需要使用特殊的語法才能表達。
在本章中你會學習到 JavaScript 裡頭各種不同定義函式的方式。首先是函式表達式
（function expressions）和函式宣告式（function declarations），接著看看函式作用域和變
數的 hoisting 是怎麼運作的。然後你就會學習到一系列的模式，幫助提升你的 API （提供
更好的函式介面）、程式碼初始化（用更少的全域變數），和效能（換句話說就是避免不
必要的工作）。
讓我們一頭栽進函式吧！首先就從回顧和澄清重要的基礎開始。
背景
JavaScript 的函式有兩個主要的特色，讓它們如此特別—第一，函式是 JavaScript 的
第一級物件（first-class object），第二是函式提供了作用域。
函式
也是物件，它們可以：
可以在執行期、程式執行的過程中動態建立
可以指定給變數、也可以將參考複製給其他變數，可以被擴充，而且除了少數的例
外情況，也可以被刪除
函式
第四章
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