JavaScript OOD

JavaScript 原型

function Person(){}

Person.prototype.name = "Nicholas";
Person.prototype.age = 29;
Person.prototype.job = "Software Engineer";
Person.prototype.sayName = function(){
    alert(this.name);
}
var p1 = new Person();
var p2 = new Person();
p1.name = "wj";
alert(p1.name);                           //wj——来自实例
alert(p2.hasOwnProperty("name"));         //true——使用hasOwnProperty()检测属性是否在实例中
alert("name" in p1);                      //true——用in判断在实例或者原型中
alert(p2.name);                           //Nicholas——来自原型
alert(p2.hasOwnProperty("name"));         //false——使用hasOwnProperty()检测属性是否在实例中
alert("name" in p2);                      //true——用in判断在实例或者原型中
delete p1.name;
alert(p1.name);                           //Nicholas——来自原型
alert(p1.hasOwnProperty("name"));         //false——使用hasOwnProperty()检测属性是否在实例中
alert("name" in p1);                      //true——用in判断在实例或者原型中


///判断是否在原型中
function hasPrototypeProperty(object, name){
    //name属性不在实例中，能够访问到name属性
    return !object.hasOwnProperty(name) && (name in object);
}

call apply用法

//每个函数都包含2个非继承而来的apply()和call()方法，这2个函数的用途都是在特定的作用域中调用
function sum(num1, num2){
    return num1 + num2;
}

function callSum1(num1,num2){
    sum.apply(this, arguments);                          //传入arguments对象
}

function callSum2(num1,num2){
    sum.apply(this, [num1,num2]);                        //传入Array
}

function callSum3(num1,num2){
    sum.call(this,num1,num2);
}
alert(callSum1(10,10));                                          //20
alert(callSum2(10,10));                                          //20
alert(callSum3(10,10));                                          //20

//真正的用法
window.color = "red";
var o = {color:"blue"};

function sayColor(){
    alert(this.color);
}

sayColor();                      //red——this.color的求值转换成了window.color的求值
sayColor.call(this);             //red——全局
sayColor.call(window);           //red——全局
sayColor.call(o);                //blue

组合使用构造函数模式和原型模式

function Person(name, age, job){
    this.name = name;
    this.age = age;
    this.job = job;
    this.friends = ["A","B"];                                 //请不要把name属性放在原型中
}

Person.prototype = {
    constructor: Person,
    sayName: function(){
        alert(this.name);
    }
};

var p1 = new Person("Nicholas",29,"Software Engineer");
var p1 = new Person("Greg",29,"Doctor");

p1.friends.push("C");
alert(p1.friends);                                          //A,B,C
alert(p2.friends);                                          //A,B
alert(p1.friends == p2.friends);                            //false
alert(p1.sayName == p2.sayName);                            //true

寄生构造函数模式

function Person(name,age,job){
    var o = new Object();
    o.name = name;
    o.age = age;
    o.job = job;
    o.sayName = function(){
        alert(this.name);
    };
    return o;
}
//该模式用法如下
function SpecialArray(){
    var values = new Array();
    values.push.apply(values,arguments);
    values.toPipedString = function(){
        return this.join("|");
    };
    return values;
}

var colors = new SpecialArray("red","blue","yellow");
alert(colors.toPipedString());             //red|blue|yellow