JavaScript can define properties and methods when defining a class, or dynamically add properties and methods after creating an object.

Dynamic addition of properties and methods is difficult to achieve in other object-oriented programming languages ????(C++, JavaScript, etc.), which is a reflection of the flexibility of JavaScript.

Create an object based on the Person class and add properties and methods to it: // Define class

<script>// 定義類
function Person(name,sex) {
    this.name=name;  // 定義一個屬性 name
    this.sex=sex;  // 定義一個屬性 sex
    this.say=function(){  // 定義一個方法 say()
        return "嗨！大家好，我的名字是 " + this.name + " ，性別是 " + this.sex + " 。";
    }
}

// 創(chuàng)建對象
var zhangsan=new Person("張三","男");
zhangsan.say();

// 動態(tài)添加屬性和方法
zhangsan.tel="029-81892332";
zhangsan.run=function(){
    return  " 我跑得很快！ ";
}

// 彈出警告框
alert("姓名："+zhangsan.name);
alert("姓別："+zhangsan.sex);
alert(zhangsan.say());
alert("電話："+zhangsan.tel);
alert(zhangsan.run());</script>