- Can be used equally well for code that will run on the server-side (most likely targeting the JVM) and on the client-side (for now, this means compiling to JavaScript). This is key for people to be able to use the language. Nowadays, a language that also comes with its own environment is unlikely to be adopted. [Unlike Haskell; like Dart]
- Strongly typed, with type inference across compilation units, i.e. not to force type declarations on "public APIs" (even if having them, most of the time, might be a good idea). [Unlike Scala; like Haskell]
- Provide rich constructs, like case classes, traits, partial functions, continuations… The world is complex, and our programs try to model it, and the right constructs make the programmer's job easier, and the code simpler. (See the simple vs. easy distinction made by Rich Hickey.) [Like Scala]
- Adhere to the off-side rule. Because syntax matters. [Like Python, Haskell, CoffeeScript, F#; unlike Scala, Dart…]
- Provide a rich data type library. [Like Scala; unlike JavaScript]
- Compilation should be fast enough that developers don't feel compiling/building as an additional, lengthy step that needs to happen before they can run code. I.e. when writing code running in the browser, programmers should be able to make a change in their editor, cmd-tab to the browser, reload the page, and see the change. [Unlike Scala]
- Don't force "object oriented" paradigms on programmers. E.g. the standard way to write a program shouldn't necessarily be to start defining a class. [Unlike Java, Scala]
