不从构造函数打印控制台日志

Question

javascript中有三个具有继承性的类。当我在中产阶级中删除super（）时，子构造函数不再打印console.log。但是，当我将super（）放入中产阶级时，将显示所有3个控制台日志。想知道为什么丢失的中间super（）甚至抵消了子控制台日志。

class Great {
    constructor() {
        console.log('this is great');
    }
}

class Grand extends Great {
    constructor() {
        // super();
        console.log('this is grand');
    }
}

class Father extends Grand {
    constructor() {
        super();
        console.log('I am your father');
    }
}

function main() {
    let dad = new Father();
}

main();

我希望控制台显示“这很盛大”和“我是你的父亲”。但是当评论中产阶级的上层人士时，唯一出现的是“这是伟大的”。

Answer 1

class Great {
  constructor() {
    console.log('this is great');
  }
}

class Grand extends Great {
  constructor() {
    // super();
    console.log('this is grand');
  }
}

class Father extends Grand {
  constructor() {
    // calls Grand constructor function and its console.log
    super();
    // ReferenceError: must call super constructor before using 'this' in derived class constructor
    // The Grand constructor throws an error preventing the next line to be executed
    console.log('I am your father');
  }
}

function main() {
  let dad = new Father();
}

main();

与以下相同：

const functionWithError = () => {
  console.log('I am about to throw');
  throw new Error('Throwing...');
}

const functionThatCallsFunctionWithError = () => {
  functionWithError();
  console.log('This console.log will never be called');
}

functionThatCallsFunctionWithError();

Answer 2

取消对Grand班上的超级选手的评论

在访问“ this”或从派生构造函数返回之前，必须在派生类中调用超级构造函数

class Great {
    constructor() {
        console.log('this is great');
    }
}

class Grand extends Great {
    constructor() {
        super();
        console.log('this is grand');
    }
}

class Father extends Grand {
    constructor() {
        super();
        console.log('I am your father');
    }
}

function main() {
    let dad = new Father();
}

main();