Web 前端頁面性能監控指標

性能監控 / 性能指標 / 性能優化

白屏時間計算

FCP

白屏時間：從瀏覽器輸入地址並回車后到頁面開始有內容的時間；

首屏時間計算

FMP

首屏時間：從瀏覽器輸入地址並回車后到首屏內容渲染完畢的時間；

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❓ Navigation Timing Level 2, W3C Working Draft 21 January 2020

https://www.w3.org/TR/navigation-timing-2/

✅ Navigation Timing, W3C Recommendation 17 December 2012

https://www.w3.org/TR/navigation-timing/

https://developer.mozilla.org/en-US/docs/Web/API/Navigation_timing_API

https://developer.mozilla.org/en-US/docs/Web/API/Navigation_timing_API/Using_Navigation_Timing

window.addEventListener("load", function() {
  let now = new Date().getTime();
  let loadingTime = now - performance.timing.navigationStart;
 
  document.querySelector(".output").innerText =
        loadingTime + " ms";
}, false);

window.addEventListener("load", function() {
  let now = new Date().getTime();
  let loadingTime = now - performance.timing.navigationStart;
   
  output = "Load time: " + loadingTime + " ms<br/>";
  output += "Navigation type: ";
 
  switch(performance.navigation.type) {
      case PerformanceNavigation.TYPE_NAVIGATE:
        output += "Navigation";
      break;
    case PerformanceNavigation.TYPE_RELOAD:
        output += "Reload";
      break;
    case PerformanceNavigation.TYPE_BACK_FORWARD:
        output += "History";
      break;
    default:
        output += "Unknown";
      break;
  }
 
  output += "<br/>Redirects: " + 
      performance.navigation.redirectCount;
  document.querySelector(".output").innerHTML = output;
}, false);

https://developers.google.com/web/fundamentals/performance/navigation-and-resource-timing