JavaScript 继承 Object.create()？

Question

如何使用 Object.create() 进行继承？我尝试了这些，但都没有用:

var B = function() {};
var A = function() {};
A = Object.create(B);
A.prototype.C = function() {};

和

var B = function() {};
var A = function() {};
A.prototype.C = function() {};
A = Object.create(B);

和

var B = function() {};
A = Object.create(B);
var A = function() {};
A.prototype.C = function() {};

没有任何效果。我应该如何使用这个新的 Object.create() 函数？

Answer 1

在 JavaScript 中有几种实现继承的方法

构造继承。在不需要调用父类(super class)型构造函数时使用:

function Rectangle(length, width) { 
    this.length = length;
    this.width = width;
}

Rectangle.prototype.getArea = function() {
    return this.length * this.width;
};

// inherits from Rectangle
function Square(size) { 
    this.length = size;
    this.width = size;
}

Square.prototype = Object.create(Rectangle.prototype);

var rect = new Rectangle(6, 8);
var square = new Square(10);

console.log(rect.getArea());                // 48
console.log(square.getArea());              // 100
console.log(rect instanceof Rectangle);     // true
console.log(rect instanceof Object);        // true
console.log(square instanceof Square);      // true
console.log(square instanceof Rectangle);   // true
console.log(square instanceof Object);      // true

构造函数窃取。如果需要调用父类(super class)型构造函数时使用:

function Rectangle(length, width) { 
    this.length = length;
    this.width = width;
}

Rectangle.prototype.getArea = function() {
    return this.length * this.width;
};

// inherits from Rectangle
function Square(size) { 
    Rectangle.call(this, size, size);
}

Square.prototype = Object.create(Rectangle.prototype);

var rect = new Rectangle(6, 8);
var square = new Square(10);

console.log(rect.getArea());                // 48
console.log(square.getArea());              // 100
console.log(rect instanceof Rectangle);     // true
console.log(rect instanceof Object);        // true
console.log(square instanceof Square);      // true
console.log(square instanceof Rectangle);   // true
console.log(square instanceof Object);      // true