# What Dart Is and Where It Runs — Dart

Source: https://www.skillbyai.com/en/dart/f-what

> Describe Dart's goals, compilation targets and relationship with Flutter.

## A client-optimised language

**Dart** is an open-source, statically typed, object-oriented language from Google, designed for building fast apps on many platforms. It is best known as the language of **Flutter**, Google's UI toolkit for Android, iOS, web, Windows, macOS and Linux, but it also runs command-line tools and servers. Dart has a flexible compilation model. During development it runs on the **Dart VM** with a **JIT** (just-in-time) compiler, enabling Flutter's **hot reload**, where code changes appear in a running app in about a second. For release builds it compiles **ahead of time (AOT)** to native ARM or x64 machine code for fast start-up and predictable performance. For the web it compiles to **JavaScript** or **WebAssembly**. **Dart 3** (2023) made **sound null safety** mandatory and added **records**, **patterns** and **class modifiers**, and later releases added features such as **extension types**. Dart's syntax will feel familiar if you know Java, C#, JavaScript or Kotlin, while its type system and tooling make it pleasant for large codebases.

## One language, several targets

Dart runs on the VM with JIT in development and compiles AOT to native code, JavaScript or WebAssembly for release.

![A central code icon with arrows to four targets: a gear for the VM, a chip for native code, a browser window and a block representing WebAssembly.](assets/figures/dart/section-1-map.svg) — Figure 1.1 — Dart's compilation targets.

## A first Dart program

Top-level main, type inference and string interpolation.

```dart
void main(List<String> args) {
  final name = args.isNotEmpty ? args.first : 'Asha';   // inferred as String
  var visits = 1;
  visits += 2;

  print('Hello, $name! You have visited $visits times.');
  print('Next year you will be ${age(2000) + 1}.');      // expression in ${}
}

int age(int birthYear) => DateTime.now().year - birthYear;

// terminal:  dart run bin/hello.dart Ravi
```

## Learn Dart before diving deep into Flutter

Flutter code is full of named parameters, const constructors, futures, streams and null-safety operators. A short focus on the language first makes widget code much easier to read.

**Quiz:** Which compilation mode does Flutter use during development to support hot reload?

- [x] JIT compilation on the Dart VM
- [ ] AOT compilation to native code
- [ ] Compilation to JavaScript only
- [ ] Interpretation without compilation

*Answer:* JIT compilation on the Dart VM. The JIT on the Dart VM allows code to be updated in a running app.