检查FinalClass的构造函数中的this.constructor，如果它不是它本身，则抛出。（借用@帕特里克Roberts对this.constructor而不是this.constructor.name的检查。

class FinalClass {
  constructor () {
    if (this.constructor !== FinalClass) {
      throw new Error('Subclassing is not allowed')
    }
    console.log('Hooray!')
  }
}

class WrongClass extends FinalClass {}

new FinalClass() //=> Hooray!

new WrongClass() //=> Uncaught Error: Subclassing is not allowed

或者，在支持的情况下，使用new.target。谢谢@loganfsmyth。

class FinalClass {
  constructor () {
    if (new.target !== FinalClass) {
      throw new Error('Subclassing is not allowed')
    }
    console.log('Hooray!')
  }
}

class WrongClass extends FinalClass {}

new FinalClass() //=> Hooray!

new WrongClass() //=> Uncaught Error: Subclassing is not allowed

正如您所说，您也可以使用装饰器来实现这种行为。

function final () {
  return (target) => class {
    constructor () {
      if (this.constructor !== target) {
        throw new Error('Subclassing is not allowed')
      }
    }
  }
}

const Final = final(class A {})()

class B extends Final {}

new B() //=> Uncaught Error: Subclassing is not allowed

正如帕特里克Roberts在评论中所分享的，装饰器语法@final仍在提议中。它可以在Babel和babel-plugin-transform-decorators-legacy中使用。

constructor.name很容易被欺骗。只需使子类与超类同名即可：

class FinalClass {
  constructor () {
    if (this.constructor.name !== 'FinalClass') {
      throw new Error('Subclassing is not allowed')
    }
    console.log('Hooray!')
  }
}

const OopsClass = FinalClass

;(function () {
  class FinalClass extends OopsClass {}

  const WrongClass = FinalClass

  new OopsClass //=> Hooray!

  new WrongClass //=> Hooray!
}())

最好检查constructor本身：

class FinalClass {
  constructor () {
    if (this.constructor !== FinalClass) {
      throw new Error('Subclassing is not allowed')
    }
    console.log('Hooray!')
  }
}

const OopsClass = FinalClass

;(function () {
  class FinalClass extends OopsClass {}

  const WrongClass = FinalClass

  new OopsClass //=> Hooray!

  new WrongClass //=> Uncaught Error: Subclassing is not allowed
}())

假设你使用的是TypeScript，最简单的方法是将构造函数设置为private，如下所示：

class MyClass {

            private constructor() {}

        }

然后，如果您尝试示例化或扩展此类，则应该得到一个编译时错误。