https://kotlinlang.org/api/core/1.9/kotlin-stdlib/kotlin.collections/flat-map.html
flatmap
https://caniuse.com/mdn-javascript_builtins_array_flatmap
"Can I use" provides up-to-date browser support tables for support of front-end web technologies on desktop and mobile web browsers.
support tablesjavascriptbuiltarrayflatmap
https://kotlinlang.org/api/core/1.4/kotlin-stdlib/kotlin.collections/flat-map.html
flatmap