装饰器

装饰器应用范围：

Classes
Class fields (public, private, and static)
Class methods (public, private, and static)
Class accessors (public, private, and static)

新的类元素

Class Auto-Accessors 通过在 class field 前面添加 accessor 关键字来创建：

js

class C {
  accessor x = 1
}

等价于

js

class C {
  #x = 1

  get x() {
    return this.#x
  }

  set x(val) {
    this.#x = val
  }
}

`addInitializer`

可以在装饰器中定义一个 addInitializer 方法，用来执行初始化逻辑。addInitializer 初始化时间取决于是何种类型的装饰器：

Class decorator initializers are run after the class has been fully defined, and after class static fields have been assigned.
Class element initializers run during class construction, before class fields are initialized.
Class static element initializers run during class definition, before static class fields are defined, but after class elements have been defined.

典型的使用场景：通过装饰器在浏览器中注册一个自定义元素