javascript - 我怎样才能实现继承链？

Question

继承有问题。如何实现从 Some Pencil 到 Another Pencil 的类型继承？需要:pen3.type//common

  class Pencil {
     constructor(color) {
      this.color = color;
    }
    intro() {
      console.log(`this is ${this.color} pencil`);
     }
    };

    class SomePencil extends Pencil {
     constructor(color, type) {
      super(color);
       this.type = type;
     }
    };
    class AnotherPencil extends SomePencil {
      constructor(color,type) {
       super(color, type);
     }
    };

    let pen1 = new Pencil();
    let pen2 = new SomePencil("red", "common");
    let pen3 = new AnotherPencil("green");

    console.log("type" in pen3); // true

Answer 1

继承只会继承属性而不是值，除非它们是在类定义本身中设置的。例如

class SomePencil extends Pencil {
 constructor(color, type) {
  super(color);
   this.type = type || 'common'; // Setting a default value if type is not passed
 }
};

设置默认值的新方法

class SomePencil extends Pencil {
 constructor(color, type = 'common') {
  super(color);
   this.type = type;
 }
};

引用jsfiddle