Manual:$wgResourceLoaderEnableJSProfiler

ResourceLoader: $wgResourceLoaderEnableJSProfiler
When enabled, execution of JavaScript modules is profiled client-side.
Introduced in version:1.32.0 (Gerrit change 444773; git #7f3c102a)
Removed in version:still in use
Allowed values:(boolean)
Default value:false

Details edit

Instrumentation happens in mw.loader.profiler. Use mw.inspect('time') from the browser console to display the data.