January 2013
Intermediate to advanced
332 pages
5h 23m
Chinese
Content preview from JAVASCRIPT網頁應用程式設計
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第九章
如果將物件傳入
values()
函式，它會回傳一組包含所有物件「屬性值」的陣列（功能剛
好和
keys()
相反）：
// 下面這行程式會回傳：[2]
values({two: 2});
善用除錯工具（Debugger）
JavaScript 的除錯工具，可說是開發 JavaScript 程式的秘技之一。它能讓你在程式裡安
插中斷點（breakpoint）、設定待觀察表達式（watch expressions）、檢查變數值，藉此看
出程式執行過程中究竟發生了些什麼事。
設定程式中斷點的做法非常簡單—只要在希望讓除錯工具暫停執行的地方，加上一行
debugger
敘述句就行了：
var test = function(){
// ...
debugger
};
第二種做法是：切換至檢查工具的「Script」頁籤、選擇某個 script 檔案、再點擊希望安
插中斷點的程式碼行號（如圖 9-10 所示）。
圖 9-10 在 Safari 的網頁檢查工具裡，設定程式的中斷點
128
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.