Manual:$wgResourceLoaderExperimentalAsyncLoading

ResourceLoader: $wgResourceLoaderExperimentalAsyncLoading
Experimental Asynchronous loading for ResourceLoader.
Introduced in version:1.19.0
Removed in version:1.26.0 (Gerrit change 232942; git #79ae8460)
Allowed values:(boolean)
Default value:false

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Experimental Asynchronous loading for ResourceLoader.