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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測試與除錯
|
159
圖 9-13 檢視每一筆網路請求的詳細分析資訊，像是請求 / 回應表頭
效能分析和計時工具
在開發較大型的 JavaScript 應用程式時，往往得對系統效能表現錙銖必較（特別是當你
的使用者會透過手機上網時）。網頁檢查工具和 Firebug 都有內建效能分析和計時工具，
這些工具能協助我們隨時精準的掌握程式的效能表現。
如果想分析某段程式碼的效能，做法很簡單—只要在希望分析效能的某段程式碼前後，
分別加上
console.profile()
和
console.profileEnd()
兩組函式就行：
console.profile();
// ...
console.profileEnd();
只要一呼叫
profileEnd()
，就會產生一組效能分析資訊，裡面會詳細列出被
console.
profile()
和
console.profileEnd()
夾住的這段程式碼中，所有被呼叫到的函式（以及
每個函式所花費的時間）。如圖 9-14 所示。
130
160
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第九章
圖 9-14 利用網頁檢查工具，分析函式執行率
你也可以使用檢查工具的「Profile」頁籤裡的
錄製
（
record
）功能，效果與你在程式碼
前後加上
console.profile()
和
console.profileEnd()
敘述句完全一樣。透過這份效能 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
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.