Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Prevent LCP being reported for hidden prerendered page #326

Merged
merged 1 commit into from
Mar 6, 2023
Merged

Prevent LCP being reported for hidden prerendered page #326

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
21 changes: 11 additions & 10 deletions src/onLCP.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -54,17 +54,18 @@ export const onLCP = (onReport: ReportCallback, opts?: ReportOpts) => {
const handleEntries = (entries: LCPMetric['entries']) => {
const lastEntry = entries[entries.length - 1] as LargestContentfulPaint;
if (lastEntry) {
// The startTime attribute returns the value of the renderTime if it is
// not 0, and the value of the loadTime otherwise. The activationStart
// reference is used because LCP should be relative to page activation
// rather than navigation start if the page was prerendered. But in cases
// where `activationStart` occurs after the LCP, this time should be
// clamped at 0.
const value = Math.max(lastEntry.startTime - getActivationStart(), 0);

// Only report if the page wasn't hidden prior to LCP.
if (value < visibilityWatcher.firstHiddenTime) {
metric.value = value;
if (lastEntry.startTime < visibilityWatcher.firstHiddenTime) {
// The startTime attribute returns the value of the renderTime if it is
// not 0, and the value of the loadTime otherwise. The activationStart
// reference is used because LCP should be relative to page activation
// rather than navigation start if the page was prerendered. But in cases
// where `activationStart` occurs after the LCP, this time should be
// clamped at 0.
metric.value = Math.max(
lastEntry.startTime - getActivationStart(),
0
);
metric.entries = [lastEntry];
report();
}
Expand Down