js 对象继承 Javascript对象继承

var book1 = { 
    name : "Javascript", 
    writeLine : function() { //from w w  w  . j a  va2s . c  om
        console.log(this.name); 
    } 
}; 

var book2 = Object.create(book1, { 
    name : { 
        configurable : true, 
        enumerable : true, 
        value : "CSS", 
        writable : true 
    } 
}); 

book1.writeLine();          // outputs "Javascript" 
book2.writeLine();          // outputs "CSS" 

console.log(book1.hasOwnProperty("writeLine"));     // true 
console.log(book1.isPrototypeOf(book2));        // true 
console.log(book2.hasOwnProperty("writeLine"));     // false 

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

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

Rectangle.prototype.toString = function() { 
    return "[Rectangle " + this.length + "x" + this.height + "]"; 
}; 

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

Square.prototype = Object.create(Rectangle.prototype, { 
                        constructor : { 
                            configurable : true, 
                            enumerable : true, 
                            value : Square, 
                            writable : true 
                        } 
                    }); 

// call the supertype method 
Square.prototype.toString = function() {  
    var text = Rectangle.prototype.toString.call(this); 
    return text.replace("Rectangle", "Square"); 
};