Node.js中的继承

摘要：借用构造函数借助或使用构造函数缺少函数复用原型链继承使用指向对象子类无法给父类传递参数无法使用字面量添加新方法所有子类对象共享父类所有方法和属性引用类型组合继承借用构造函数对实例属性继承对共享方法继承会调用两次父类构造函数继承

借用构造函数,借助call或apply,使用Superclass构造函数,缺少函数复用

function Superclass(name = "default") {
        this.name = name;
    }
    
    function Subclass(age = 22, name) {
        this.age = age;
        Superclass.call(this, name);
        this.say = function () {
            console.log(`this.name=${this.name}...this.age=${this.age}`);
        };
    }
    
    const test = new Subclass(23);
    test.say();
    console.log(`test instanceof Subclass`, test instanceof Subclass);
    console.log(`test instanceof Superclass`, test instanceof Superclass);
    console.log(test.__proto__.constructor);
    console.log(Subclass.prototype.constructor);

原型链继承,使用prototype指向Superclass对象,子类无法给父类传递参数,无法使用字面量添加新方法,所有子类对象共享父类所有方法和属性(引用类型)

    function Superclass(name = "default") {
        this.name   = name;
        this.colors = ["r", "y"];
    }

    function Subclass(age = 22) {
        this.age = age;
        this.say = function () {
            console.log(`this.name=${this.name}...this.age=${this.age}`);
        };
    }

    Subclass.prototype             = new Superclass();
    Subclass.prototype.constructor = Subclass;

    const test  = new Subclass(23);
    const test1 = new Subclass(24);
    test.colors.push("b");
    console.log(test.colors);
    console.log(test1.colors);
    test.say();
    test1.say();
    console.log(`test instanceof Subclass`, test instanceof Subclass);
    console.log(`test instanceof Superclass`, test instanceof Superclass);
    console.log(test.__proto__.constructor);
    console.log(Subclass.prototype.constructor);

组合继承,prototype+call/apply,借用构造函数对实例属性继承,prototype对共享方法继承,会调用两次父类构造函数

    function Superclass(name = "default") {
        this.name = name;
    }

    Superclass.prototype.say = function () {
        console.log(this.name);
    };

    function Subclass(age = 22, name) {
        this.age = age;
        Superclass.call(name);
    }

    Subclass.prototype             = new Superclass();
    Subclass.prototype.constructor = Subclass;

    const test = new Subclass(23);
    test.say();
    console.log(`test instanceof Subclass`, test instanceof Subclass);
    console.log(`test instanceof Superclass`, test instanceof Superclass);
    console.log(test.__proto__.constructor);
    console.log(Subclass.prototype.constructor);

ES6 Class继承

    class Superclass {
        constructor(name = "default") {
            this.name = name;
        }
    }
    class Subclass extends Superclass {
        constructor(age = 22, name) {
            super(name);
            this.age = age;
        }

        say() {
            console.log(`this.name=${this.name}...this.age=${this.age}`);
        }
    }

    const test = new Subclass(23);
    test.say();
    console.log(`test instanceof Subclass`, test instanceof Subclass);
    console.log(`test instanceof Superclass`, test instanceof Superclass);
    console.log(test.__proto__.constructor);
    console.log(Subclass.prototype.constructor);

Node util.inherits;

    function Superclass(name = "default") {
        this.name = name;
    }

    function Subclass(age = 22, name) {
        this.age = 22;
        Superclass.call(this, name);

        this.say = function () {
            console.log(`this.name=${this.name}...this.age=${this.age}`);
        };

    }

    require("util").inherits(Subclass, Superclass);

    const test = new Subclass(23);
    test.say();
    console.log(`test instanceof Subclass`, test instanceof Subclass);
    console.log(`test instanceof Superclass`, test instanceof Superclass);
    console.log(test.__proto__.constructor);
    console.log(Subclass.prototype.constructor);