控制台日志未从构造函数打印

Question

javascript中有三个具有继承性的类。 当我删除中产阶级中的 super(( 时，子构造函数不再打印控制台.log。 但是当我把 super(( 放在中产阶级时，就会出现所有 3 个控制台日志。 想知道为什么缺少中间的super((甚至会取消子控制台日志。

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"这很宏伟"和"我是你的父亲"。 但唯一出现的是"这很宏伟"，在评论中产阶级的超级时。

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();

它与以下内容相同：

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

取消注释 class Grand 中的超级

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();