15 cool features of Dart

I wrote an answer on programmers.stackoverflow.com for the question "What are some useful features of the Dart programming language?"

The answer, or 13 answers, was too epic to be contained. It is copied here for your reading enjoyment. (Like the answer? Please vote it up. Thanks!)

1) Optional static types. When I'm prototyping or simply writing small scripts, I don't use a ton of static types. I just don't need 'em, and I don't want to get bogged down with the ceremony. However, some of those scripts evolve into bigger programs. As the scripts scale, I tend to want classes and static type annotations.

2) Innocent until proven guilty. Dart tries hard to minimize the situations that result in a compile-time error. Many conditions in Dart are warnings, which don't stop your program from running. Why? In keeping with web development fashion, it's imperative to allow developers to try a bit of code, hit reload, and see what happens. The developer shouldn't have to first prove the entire program is correct before just testing a corner of the code.

3) Lexical scope. This is awesome, if you're not used to it. Simply put, the visibility of variables, and eventhis, is defined by the program structure. This eliminates a class of puzzlers in traditional web programming. No need to re-bind functions to keep this to what you think or expect.

4) Real classes baked into the language. It's clear most developers want to work in classes, as most web development frameworks offer a solution. However, a "class" from framework A isn't compatible with framework B, in traditional web development. Dart uses classes naturally.

5) Top-level functions. One painful part of Java is that everything has to be put into a class. This is a bit artificial, especially when you want to define a few utility functions. In Dart, you can define functions at the top level, outside of any class. This makes library composition feel more natural.

6) Classes have implicit interfaces. The elimination of explicit interfaces simplifies the language. No more need to define IDuck everywhere, all you need now is a class Duck. Because every class has an implicit interface, you can create a MockDuck implements Duck

7) Named constructors. You can give constructors names, which really helps with readibility. For example: var duck = new Duck.fromJson(someJsonString)

8) Factory constructors. The factory pattern is quite common, and it's nice to see this baked into the language. A factory constructor can return a singleton, an object from a cache, or an object of a sub-type.

9) Isolates. Gone are the days of sharing mutable state between threads (an error prone technique). A Dart isolate is an isolated memory heap, able to run in a separate process or thread. Isolates communicate by sending messages over ports. Isolates work in the Dart VM and can compile to Web workers in HTML5 apps.

10) Dart compiles to JavaScript. This is critically important, as JavaScript is the lingua franca of the web. Dart apps should run across the modern web.

11) Strong tooling. The Dart project also ships an editor. You'll find code completion, refactoring, quick fixes, code navigation, debugging, and more. Also, IntelliJ has a Dart plugin.

12) Libraries. You can organize Dart code into libraries, for easier namespacing and reusability. Your code can import a library, and libraries can re-export.

13) String interpolation. This is just a nice feature, making it easy to compose a string: var msg = "Hello $friend!";

14) noSuchMethod Dart is a dynamic language, and you can handle arbitrary method calls withnoSuchMethod()

15) Generics. Being able to say "this is a list of apples" gives your tools much more info to help you and catch potential errors early. Luckily, though, Dart's generics are more simple that what you're probably used to.