JS DCR/Tree shaking VS Dart2JS

animals.dart

main() {
  var dog = new Dog('Mitzie');
  dog.speak();
}

class Animal {
  var name;
  Animal(this.name);
  
  speak() => print('$name makes a noise.');
}

class Dog extends Animal {
  Dog(name) : super(name);
  speak() => print('$name barks.');
}

class Cat extends Animal {
  Cat(name) : super(name);
  speak() => print('$name meows.');
}

animals.js

class Animal { 
  constructor(name) {
    this.name = name;
  }
  
  speak() {
    console.log(`${this.name} makes a noise.`);
  }
}

class Dog extends Animal {
  speak() {
    console.log(`${this.name} barks.`);
  }
}

class Cat extends Animal {
  speak() {
    console.log(`${this.name} meows.`);
  }
}

var dog = new Dog('Mitzie');
dog.speak();

output_babili.js

// 195 characters/bytes
class Animal{constructor(a){this.name=a}speak(){console.log(`${this.name} makes a noise.`)}}class Dog extends Animal{speak(){console.log(`${this.name} barks.`)}}var dog=new Dog('Mitzie');dog.speak();

output_dart2js.js

// 48 characters/bytes 
main: function() {
  P.print("Mitzie barks.");
}

output_rollup.js

class Animal { 
  constructor(name) {
    this.name = name;
  }
  
  speak() {
    console.log(`${this.name} makes a noise.`);
  }
}

class Dog extends Animal {
  speak() {
    console.log(`${this.name} barks.`);
  }
}

var dog = new Dog('Mitzie');
dog.speak();