javascript - JS 对象继承与属性

Question

我试图为我的项目获得一个非常简单的继承模式，从基类扩展到专门的类。但是，我的专业类的属性正在被父类的属性覆盖。

这是为什么？我该如何解决？

谢谢

function Ship(className, x, y){
    this.className = className;
    this.x = x;
    this.y = y;
    this.speed = 0;
}

function Corvette(className, x, y){
    this.className = className;
    this.x = x;
    this.y = y;    
    this.speed = 100;        
    Ship.call(this, className, x, y)
}


Corvette.prototype = Object.create(Ship.prototype);   

var ship = new Ship("Biggie", 50, 50);
var corvette = new Corvette("Smallish", 50, 50);

console.log(Corvette.className) // "Smallish" - correct via parameter.
console.log(Corvette.speed) // should be 100, is 0 - not correct, "static" from parent attribute
console.log(Corvette.constructor.name) // Ship

Answer 1

为什么子对象中的属性与父对象中已有的属性相同？

我建议你这样做

function Ship(className, x, y, speed = 0) {
    this.className = className;
    this.x = x;
    this.y = y;
    this.speed = speed;
}

function Corvette(className, x, y, speed = 100) { 
    Ship.call(this, className, x, y, speed);
}

Corvette.prototype = Object.create(Ship.prototype);   
Corvette.prototype.constructor = Corvette;

var ship = new Ship("Biggie", 50, 50);
var corvette = new Corvette("Smallish", 50, 50);

console.log(corvette.className) // "Smallish" - correct via parameter.
console.log(corvette.speed) // should be 100, is 0 - not correct, "static" from parent attribute
console.log(corvette.constructor.name) // Ship

如果您的浏览器支持 ES6 的某些功能，请使用此功能 ES6 classes 。

class Ship { // And also Ship is an abstractionm so you can use `abstract` keyword with it
  constructor(className, x, y, speed = 0) {
    this.className = className;
    this.x = x;
    this.y = y;
    this.speed = speed;
  }
}

class Corvette extends Ship {
   constructor(className, x, y, speed = 100) {
        super(className, x, y, speed);
   }
}

var ship = new Ship("Biggie", 50, 50);
var corvette = new Corvette("Smallish", 50, 50);

console.log(corvette.className) // "Smallish" - correct via parameter.
console.log(corvette.speed) // should be 100, is 0 - not correct, "static" from parent attribute
console.log(corvette.constructor.name) // Ship