Question

在定义子类时，我得到了TypeErorr：undefined用于构造函数参数，正如我所见，它充当占位符。到底发生了什么以及如何解决它？

function Class(object) {
    this.name = object.name;
}

var myClass = new Class({
    name: "ClassName"
})

console.log(myClass.name); 

function SubClass(object) {
    this.name = object.name;
}

SubClass.prototype = new Class();
SubClass.prototype.constructor = SubClass;

var mySubClass = new SubClass({
    name: "SubClassName"
})

// TypeError：object is undefined

Answer 1

通常你的基类会在其原型上有方法，所以使用SubClass.prototype = Object.create(BaseClass.prototype)更合适，并在基类的构造函数中调用你的父构造函数，以便找到object.name在父构造函数中（这是你得到的错误，因为没有任何内容传递到SubClass.prototype = new Class()。

function Class(object) {
    this.name = object.name;
}

Class.prototype.sayName = function () {
    return this.name;
}

var myClass = new Class({
    name: "ClassName"
});

console.log(myClass.name); 

function SubClass(object) {
    // call parent constructor with context of the new SubClass instance
    Class.call(this, object);
}

SubClass.prototype = Object.create(Class.prototype);
SubClass.prototype.constructor = SubClass;

var mySubClass = new SubClass({
    name: "SubClassName"
});

console.log(mySubClass.sayName());
// > "SubClassName"

以下是一些有用的参考资料

子类不继承超类属性

1 个答案: