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创建实例时出错

重要程度: 5

这里有一份 Rabbit 扩展 Animal 的代码。

不幸的是，Rabbit 对象无法被创建。是哪里出错了呢？请解决它。

class Animal {

  constructor(name) {
    this.name = name;
  }

}

class Rabbit extends Animal {
  constructor(name) {
    this.name = name;
    this.created = Date.now();
  }
}

let rabbit = new Rabbit("White Rabbit"); // Error: this is not defined
alert(rabbit.name);

这是因为子类的 constructor 必须调用 super()。

这里是修正后的代码：

class Animal {

  constructor(name) {
    this.name = name;
  }

}

class Rabbit extends Animal {
  constructor(name) {
    super(name);
    this.created = Date.now();
  }
}

let rabbit = new Rabbit("White Rabbit"); // 现在好了
alert(rabbit.name); // White Rabbit

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