PerformanceNavigationTiming: domContentLoadedEventStart property
The domContentLoadedEventStart
read-only property returns a DOMHighResTimeStamp
representing the time immediately before the current document's DOMContentLoaded
event handler starts.
Typically frameworks and libraries wait for the DOMContentLoaded
event before starting to run their code. We can use the domContentLoadedEventStart
and the domContentLoadedEventEnd
properties to calculate how long this takes to run.
Value
A DOMHighResTimeStamp
representing the time immediately before the current document's DOMContentLoaded
event handler starts.
Examples
Measuring DOMContentLoaded
event handler time
The domContentLoadedEventStart
property can be used to measure how long it takes process the DOMContentLoaded
event handler.
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 domContentLoadedTime =
entry.domContentLoadedEventEnd - entry.domContentLoadedEventStart;
console.log(
`${entry.name}: DOMContentLoaded processing time: ${domContentLoadedTime}ms`
);
});
});
observer.observe({ type: "navigation", buffered: true });
Example using Performance.getEntriesByType()
, which only shows navigation
performance entries present in the browser's performance timeline at the time you call this method:
js
const entries = performance.getEntriesByType("navigation");
entries.forEach((entry) => {
const domContentLoadedTime =
entry.domContentLoadedEventEnd - entry.domContentLoadedEventStart;
console.log(
`${entry.name}: DOMContentLoaded processing time: ${domContentLoadedTime}ms`
);
});
Specifications
Specification |
---|
Navigation Timing Level 2 # dom-performancenavigationtiming-domcontentloadedeventstart |
Browser compatibility
BCD tables only load in the browser