The loadEventStart
read-only property returns a DOMHighResTimeStamp
representing the time immediately before the current document's load
event handler starts.
The loadEventStart
read-only property returns a DOMHighResTimeStamp
representing the time immediately before the current document's load
event handler starts.
A DOMHighResTimeStamp
representing the time immediately before the current document's load
event handler starts.
load
event handler timeThe loadEventStart
property can be used to measure how long it takes process theload
event handler.
This is useful to measure the time of long running load
event handlers.
js
window.addEventListener("load", (event) => { // Some long running code });
Example using a PerformanceObserver
, which notifies of new navigation
performance entries as they are recorded in the browser's performance timeline. Use the buffered
option to access entries from before the observer creation.
js
const observer = new PerformanceObserver((list) => { list.getEntries().forEach((entry) => { const loadEventTime = entry.loadEventEnd - entry.loadEventStart; if (loadEventTime > 0) { console.log(`${entry.name}: load event handler time: ${loadEventTime}ms`); } }); }); observer.observe({ type: "navigation", buffered: true });
Example using Performance.getEntriesByType()
, which only shows navigation
performance entries present in the browser's performance timeline at the time you call this method:
js
const entries = performance.getEntriesByType("navigation"); entries.forEach((entry) => { const loadEventTime = entry.loadEventEnd - entry.loadEventStart; if (loadEventTime > 0) { console.log(`${entry.name}: load event handler time: ${loadEventTime}ms`); } });
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
loadEventStart |
57 | 12 | 58 | 11 | 44 | 15 | 57 | 57 | 58 | 43 | 15.1 | 7.0 |
load
event
© 2005–2023 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/PerformanceNavigationTiming/loadEventStart