我正在学习有关创建新类,扩展它和子类化的知识.我不了解以下内容：

>为什么在示例2中扩展类时,constructor()和super()都使用length作为参数？
>如果示例2中的super()应该访问父类Polygon,那么它不应该使用高度和宽度作为参数来访问Polygon类中的父类而不是长度(就像示例4中那样)吗？如果没有,为什么？

源代码是：https://googlechrome.github.io/samples/classes-es6/index.html

// Example 1: Creating a new class (declaration-form)
// ===============================================================

class Polygon {
  constructor(height,width) {
    this.name = 'Polygon';
    this.height = height;
    this.width = width;
  }
  sayName() {
    console.log('Hi,I am a ',this.name + '.');
  }

  sayHistory() {
    console.log('"Polygon" is derived from the Greek polus (many) ' +
      'and gonia (angle).');
  }
}


// Example 2: Extending an existing class
// ===============================================================

class Square extends Polygon {
  constructor(length) {
    super(length,length);
    this.name = 'Square';
  }
  get area() {
    return this.height * this.width;
  }
  set area(value) {
    this.area = value;
  }
}

let s = new Square(5);

s.sayName();
console.log('The area of this square is ' + s.area);

// Example 4: Subclassing methods of a parent class
// ===============================================================

class Rectangle extends Polygon {
  constructor(height,width) {
    super(height,width);
    this.name = 'Rectangle';
  }
  sayName() {
    console.log('Sup! My name is ',this.name + '.');
    super.sayHistory();
  }
}

let r = new Rectangle(50,60);
r.sayName();