TypeScript getter setter convention

Question

What is the convention (standard) in TypeScript for class attributes?

In the angular 2 demo (The Heroes Tour from angular.io) all attributes are set to public :

export class Hero {
   id: number;
   name: string;
}

So they can be instanciated both ways :

var hero: Hero = new Hero();
hero.id = 0;
hero.name = "hero";

or

var hero2: Hero = {id : 0, name: "hero"};

Is there a Java style convention (like this) :

export class Hero {
   private id: number;
   private name: string;

   setId(id: number): Hero {
      this.id = id;
      return this;
   }

   setName(name: string): Hero {
      this.name = name;
      return this;
   }

   getId(): number {
      return this.id;
   }

   getName(): string {
      return this.name;
   }
}

Declaration (exemple) :

var hero: Hero = new Hero();
hero.setId(0).setName('hero');

var hero2: Hero = new Hero().setId(0).setName('hero');

Solution

Java is a statically compiled language. In Java, if you publish a .jar library with a class

class Foo {
  public int bar;
}

and later decide to introduce a logic around that field

class Foo {
  private int _bar;
  public int getBar() { return _bar - 1; }
  public void setBar(int v) { _bar = v + 1; }
}

any code that uses your .jar will break and will have to be updated and re-compiled. This is why it's a big no-no in Java to expose raw public fields.

TypeScript is a superset of JavaScript which is a dynamic language. All linking is dynamic. You can safely release a library with a class

class Foo {
  bar: number
}

If you later release an update

class Foo {
  private _bar: number
  get bar() { return this._bar - 1 }
  set bar(v: number) { this._bar = v + 1 }
}

your library users won't notice.

Comments

[Laurent Schwitter]

Nobody forbids you from doing that but it's not the convention and it's overdeclarative and can get pretty ugly very quickly

[Marty]

This approach actually answers the OP's question and is accurate with a reasonable caution, and is referenced in the TypeScript docs typescriptlang.org/docs/handbook/classes.html#accessors