These are incomplete notes and thoughts on programming languages through lens of multiplatform support and coding GUI apps for platforms like Android, iOS, Mac, Windows, Linux, and web (front and back ends).
JavaScript
Lack type safety.
Java, Go, Python, Ruby, C++, C, Elixir
Not great for frontend web dev.
D
Not great for Android or iOS. Can build web apps via compiling to WASM (pretty sure it's experimental), but lack mature frameworks for frontend web dev. Not very popularly used, unfortunately.
TypeScript
It's JavaScript but with a brilliant aftermarket type system retrofit. If you must code JS, then TS is a fantastic upgrade.
For backend, there's faster languages (Java, Go). For device native apps, other languages are maybe better suited (Swift, Kotlin, etc). Great choice for web frontend.
For frontend web dev, used with React is popular. There's React Native to build device native apps for Macs, Windows, Linux, Android, and iOS that uses platform native UI widgets (some haven't reached 1.0 yet though, if you're looking for maturity). You'd still have to build 5 specialized UIs though (6 including web), and there are faster device native languages.
Kotlin
Compiles to JVM, JS, and native. Kotlin Multiplatform Mobile (alpha) is great for write-once application logic for iOS / Android native apps, but the UI code must be specialized for each platform (could still be written in Kotlin though).
e.g. Use with Google Android's Jetpack Compose (beta) and Apple's Swift UI for native Android and iOS UI.
e.g. Use with Jetbrains' Compose for Desktop to build apps for Windows, Macs, and Linux --- but this runs on JVM and renders using Skia, so it doesn't use platform native UI widgets (it draws it's own like a game does). And it's in alpha.
Some say Jetpack Compose is Google Android team's answer to Google Ads team's Dart/Flutter.
Kotlin/JS means you can use with React for frontend web dev too. Not sure of its maturity. Kotlin is great for backend using Spring or Ktor.
PHP
Not great for device native apps
C#
Windows centric. Blazor lets you do frontend web dev by compiling to WASM but it adds C#'s runtime to your web app to run in WASM as well (read: bigger, slower app).
Rust
Lower level, like C or C++. Can build web apps via compiling to WASM, but without bringing a runtime along for the ride (check out Yew or Seed). Can build backend stuff (check out Actix-web or Rocket), but frameworks aren't mature the way Django or RoR are.
Coding device native GUI apps is... not there yet.
Rust is getting a lot of traction for systems programming though (unlike D, unfortunately).
Dart
Basically exists for Flutter. Flutter lets you build apps for Windows, Macs, Linux, iOS, Android, and the web. On the web, it draws into a canvas. On devices, it renders using Skia. So it doesn't use platform native UI widgets anywhere, and draws it's own like a game does. On the web, it's UI performance is a little janky.
Dart compiles to JS or runs on Dart VM. Unlike the Kotlin stuff above, Flutter is production ready and being used by Google, notably by their Ads team (apparently some of the Kotlin stuff above are the Android team's answer to Flutter).
It's from Google, so who knows if they'll cancel it in 5 years time.
Other thoughts
Rendering to Skia like Compose for Desktop and Flutter is not great for accessibility, and their accessibility features are currently WIP.
React Native has edge cases for each platform so you'd still need to know each platform carefully. Plus TypeScript / JavaScript bridging into native can have performance issues.
Nothing's perfect.
That's all I've got time for today!
Missing: Scala, Clojure, Haskell, F#, Crystal, PureScript, Elm.