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Table of Contents
如何開始一次性能記錄
怎么看關(guān)鍵指標和瓶頸
常見問題定位方法
幾個實用小技巧
Home Web Front-end Front-end Q&A How to use browser developer tools performance tab

How to use browser developer tools performance tab

Jul 02, 2025 am 12:14 AM

打開 Performance 面板可直接查看頁面加載過程中的性能問題,是優(yōu)化頁面性能的關(guān)鍵手段。1. 開始記錄:點擊錄制按鈕或快捷鍵 Ctrl+E,進行操作后停止錄制,即可看到包含腳本、渲染、網(wǎng)絡(luò)請求等事件的時間軸;2. 查看關(guān)鍵指標:關(guān)注 FCP、LCP 和 TTI 等核心指標,判斷頁面加載速度與交互準備時間;3. 定位瓶頸:通過長任務(wù)、強制同步布局、資源過大、頻繁 layout/paint 操作等線索識別性能問題;4. 使用火焰圖、放大時間段、對比不同版本等技巧輔助分析。掌握這些步驟能有效提升性能排查效率。

打開瀏覽器開發(fā)者工具的 Performance 標簽,其實是做頁面性能優(yōu)化最直接也最有用的方式之一。它能告訴你頁面加載過程中都發(fā)生了什么,哪里卡了、哪里慢了、資源怎么分布的。

下面幾個部分,是使用 Performance 面板時你最可能關(guān)心的事,也是實際工作中排查性能問題的關(guān)鍵點。


如何開始一次性能記錄

Performance 標簽的核心功能是“錄制”頁面在一段時間內(nèi)的行為。操作很簡單:

  • 打開 DevTools(F12 或右鍵檢查)
  • 切換到 Performance 標簽
  • 點擊左上角的圓形“錄制”按鈕(或快捷鍵 Ctrl+E)
  • 進行你要分析的操作(比如刷新頁面、點擊某個按鈕)
  • 再次點擊停止錄制

這時候你會看到一個時間軸,里面包含了加載過程中的各種事件:腳本執(zhí)行、渲染、網(wǎng)絡(luò)請求等。

小技巧:如果你只想看頁面首次加載的表現(xiàn),可以勾選“Disable cache”再刷新頁面,這樣模擬的是用戶第一次訪問的情況。


怎么看關(guān)鍵指標和瓶頸

記錄完成后,Performance 會展示一張詳細的時間線圖。你可以從以下幾個方面入手:

  • FCP(First Contentful Paint):第一個內(nèi)容繪制時間,表示頁面開始有東西出現(xiàn)的時間點。
  • LCP(Largest Contentful Paint):最大內(nèi)容繪制時間,通常影響用戶感知加載速度。
  • TTI(Time to Interactive):頁面變得完全可交互的時間,也就是主線程空閑下來的時候。

這些指標都會以橙色或藍色的小標記顯示在圖表頂部。你可以通過它們大致判斷頁面是否“夠快”。

如果你發(fā)現(xiàn)某段時間主線程被大量 JS 占據(jù),那可能是腳本執(zhí)行太重了;如果網(wǎng)絡(luò)請求很多且耗時長,那可能是資源太大或者請求數(shù)太多。


常見問題定位方法

Performance 圖表中有一些明顯的線索可以幫助你發(fā)現(xiàn)問題:

  • 長任務(wù)(Long Tasks):紅色條塊表示主線程阻塞超過50ms的任務(wù),這可能導致頁面卡頓。
  • 頻繁的強制同步布局(Forced Synchronous Layout):如果有黃色警告提示,說明代碼中有觸發(fā)回流的設(shè)計問題。
  • 過大的 JS/CSS 文件:查看 Network 區(qū)域,看看主資源是否過大,有沒有壓縮空間。
  • 過多的 layout/paint 操作:頻繁的渲染動作可能意味著 DOM 操作不當或動畫設(shè)計不合理。

建議每次分析完記錄后,先從主線程活動入手,再結(jié)合網(wǎng)絡(luò)面板看看資源加載情況。


幾個實用小技巧

  • 使用火焰圖快速識別熱點:火焰圖中每一層代表一個函數(shù)調(diào)用棧,越寬表示耗時越久??梢杂脕碚页鰣?zhí)行時間最長的函數(shù)。
  • 放大特定時間段觀察細節(jié):鼠標拖動上方時間軸可以聚焦到某一秒內(nèi),方便深入分析。
  • 對比不同版本的表現(xiàn)差異:比如改了一個組件之后,錄兩次 Performance,對比兩個結(jié)果,更容易看出改動是否有性能收益。

基本上就這些。別被一堆圖表嚇住,一開始只需要關(guān)注主線程和幾個核心指標就夠了。慢慢你會發(fā)現(xiàn),這個面板其實挺直觀的,而且信息量非常大。

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