javascript面向对象编程

javascript面向对象编程的四种方式

1. 字面量方式定义对象

主要应用于属性多的对象。直接创建一个对象。

<script>            //1. 按照字面量方式 定义对象            var student = {"sname":"tom","sex":"",                "getsname":function(){return this.sname},                "setsex":function(arg){this.sex=arg}                };            console.log(student.sname);            console.log(student.getsname());            student.setsex("f");            console.log(student.sex);</script>

2.工厂方法

存在一个工厂，每次调用都可以生成一个对象。

    function getStudent(_sname,_sex)            {                var student = new Object();                student.sname=_sname;                student.sex=_sex;                student.getsname=function(){                    return this.sname;                }                student.setsname = function(_sname)                {                    this.sname=_sname;                }                return student;            }            var student = getStudent("hah","aha");//          student.setsname("jack");            console.log(student.getsname());

3.构造方法

function Student(_sname,_sex)            {                this.sname=_sname;                this.sex=_sex;                this.getsname=function()                {                    return this.sname;                }                this.setsname=function(_sname)                {                    this.sname=_sname;                }            }            var student = new Student("this","that");//          student.setsname("blue");            console.log(student.getsname());

4.通过原型的方式

function Student(){}            Student.prototype.sname="tom";            Student.prototype.sex="m";            Student.prototype.setsname=function(_sname)            {                this.sname=_sname;            }            Student.prototype.getsname=function()            {                return this.sname;            }            var student = new Student();            student.setsname("yuanxing");            var student2 = new Student();            student2.setsname("diergename");            console.log(student.getsname());            console.log(student2.getsname());

很多时候需要将 34中方法结合使用，例如

function Student(_sname,_sex)            {                this.sname=_sname;                this.sex=_sex;                Student.prototype.setsname=function(_sname)                {                    this.sname=_sname;                }                Student.prototype.getsname=function()                {                    return this.sname;                }            }                var student = new Student("hhe","m");                console.log(student.getsname());                student.setsname("xixi");                console.log(student.getsname());

下面是两个练习：
练习1：扩展Date类，添加getday1（dnum），0->星期日，1->星期一

Date.prototype.getDay1 = function(){                var day = this.getDay();                switch(day)                {                    case 0:return "星期日";                    case 1:return "星期1";                    case 2:return "星期2";                    case 3:return "星期3";                    case 4:return "星期4";                    case 5:return "星期5";                    case 6:return "星期6";                }            }            var now = new Date();            console.log(now.getDay1());

练习2：扩展string类，trim1（） 去字符串前后空格 不去中间空格

var str = "   a b c e   ";            String.prototype.trim1 = function()            {                var str = this.toString();//              while(str.charAt(0)==" ")//              {//                  //截掉第一个空格   //                  str = str.substring(1,str.length);//              }//              while(str.charAt(str.length-1)==" ")//              {//                  str = str.substr(0,str.length-1);//              }//              正则表达式的方法也可以                str = str.replace(/^\s*|\s*$/g,"");                return str;            }            console.log(str.trim1().length);