理想的继承范式——寄生组合式继承

window.onload = function() {
    var person1 = new SubType("Gee", 20);
    var person2 = new SubType("Key", 21);

    person1.colors.push("yellow");
    alert("person1: " + person1.colors);    // red, blue, green, yellow
    alert("person2: " + person2.colors);    // red, blue, green

    person1.sayName();    // Gee
    person2.sayAge();    // 21
};

function object(o){
    function F() {}
    F.prototype = o;
    return new F();
}

/**
 * 继承超类型的方法
 * @param  {Object} subType   子类型
 * @param  {Object} superType 超类型
 * @return {null}
 */
function inheritPrototype(subType, superType) {
    var prototype = object(superType.prototype);    // 创建对象
    prototype.constructor = subType;    // 增强对象
    subType.prototype = prototype;    // 指定对象
}

function SuperType(name) {
    this.name = name;
    this.colors = ["red", "blue", "green"];
}

SuperType.prototype.sayName = function() {
    alert(this.name);
};

function SubType(name, age) {
    SuperType.call(this, name);    // 继承属性，并传递参数，子类型将具有独立属性而非共享属性

    this.age = age;
}

inheritPrototype(SubType, SuperType);

SubType.prototype.sayAge = function () {
    alert(this.age);
};