Javascript中的继承。我是否继承对象的方法？如何获得结果？

debugcn 发表于 Dev

天空

我尝试在Javascript中行使继承性。从汽车继承的eCar从汽车继承的汽车。但似乎我无法将方法“ getInfo（）”用于Car或eCar-Object。如果我在浏览器中执行此操作，则结果为：

Manufacture: Siemens

undefined
undefined

我要搜索的是：

Manufacture: Siemens
Manufacture: VW
Manufacture: Tesla

。

function Vehicle(herst){

    this.manuf = herst;
}

Vehicle.prototype.getInfo = function(){
    return 'Manufacture: '+ this.manuf+'<br>';
}


Car.prototype = Vehicle;
Car.prototype.construtor = Vehicle;
Car.prototype.getInfo = Vehicle;


function Car(){ }

eCar.prototype = Car;
eCar.prototype.construtor = Car;
eCar.prototype.getInfo = Car;

function eCar(){ }


Train = new Vehicle('Siemens');
document.write(Train.getInfo()+"<br>");


Golf = new Car('VW');
document.write(Golf.getInfo()+"<br>");


Tesla = new eCar('Tesla');
document.write(Tesla.getInfo()+"<br>");

保罗·S。

您很亲密，只需要几件事就可以有所不同。

// Vehicle
function Vehicle(herst){
    this.manuf = herst;
}
Vehicle.prototype.getInfo = function () {
    return 'Manufacture: '+ this.manuf+'<br>'; // you really want to return HTML?
};
Vehicle.prototype.construtor = Vehicle;

// Car
function Car(){
    Vehicle.apply(this, arguments); // extends Vehicle
}
Car.prototype = Object.create(Vehicle.prototype); // inherits Vehicle's prototype
Car.prototype.construtor = Car;

// eCar
function eCar(){ // constructors usually start with a capital
    Car.apply(this, arguments); // extends Car
}
eCar.prototype = Object.create(Car.prototype);
eCar.prototype.construtor = eCar;

// use it

var Train = new Vehicle('Siemens'), // variables usually start lower case
    Golf = new Car('VW'),
    Tesla = new eCar('Tesla');

我选择Object.create设置继承，有些人喜欢使用的格式，Bar.prototype = new Foo()但是我觉得这会Foo在错误的时间调用构造函数。

看起来像什么？

var foo = new eCar('Foo');
foo instanceof eCar;    // foo has eCar's prototype
                        // eCar was used to construct foo
foo instanceof Car;     // foo inherited Car's prototype via eCar's prototype
                        // at the beginning of eCar, Car was applied to foo
foo instanceof Vehicle; // foo inherited Vehicle's prototype via Car's prototype
                        // at the beginning of Car, Vehicle was applied to foo
/*
    So `foo` has own properties as assigned by Vehicle, then Car, then eCar,
    and it has the prototype from eCar which shadows the prototype from Car
    which again shadows the prototype from Vehicle
*/

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