宝塔服务器面板，一键全能部署及管理，送你10850元礼包，点我领取

第一种算是比较常见了,通过闭包Store Value从而实现accessor,适用于所有浏览器.
复制代码 代码如下:
function Sandyval){
var value = val;
this.getValue = function){
return value;
};
this.setValue = functionval){
value = val;
};
}
//usage
var sandy = new Sandy”test”);
sandy.value
// => undefined
sandy.setValue”test2″)
sandy.getValue

下面是JavaScript权威指南（中文第五版）中P152页使用闭包的一个例子.
复制代码 代码如下:
function makePropertyo, name, predicate) {
var value; //This is property value;

//The setter method simply returns the value
o[‘get’ + name] = function) { return value;};

//The getter method stores the value or throws an exception if
//the predicate rejects the value
o[‘set’ + name] = functionv) {
if predicate && !predicatev) {
throw ‘set’ + name + ‘: invalid value ‘ + v;
} else {
value = y;
}
}
}

//The following code demenstrates the makeProperty) method
var o = {}; // Here is an empty object

//Add property accessor methods getName and setName
//Ensure that only string values are allowed
makePropertyo, ‘Name’, functionx) { return typeof x == ‘string’; });

o.setName’Frank’); 　　//Set the property value;
printo.getName)); 　　//Get the property value
o.setName0); //Try to set a value of the wrong type

第二种方法是使用__defineSetter__与__defineGetter__来实现accessor,看下划线就知道它们并非标准,适用于Firefox 2.0+, Safari 3.0+, Google Chrome 1.0+ 和 Opera 9.5+ ,方法使用见MDN.
复制代码 代码如下:
function Sandyval){
var value = val,
_watch = functionnewVal) {
console.log’val is Changed to : ‘ + newVal);
}

this.__defineGetter__”value”, function){
return value;
});

this.__defineSetter__”value”, functionval){
value = val;
_watchval);
});
}

var sandy = new Sandy”test”);
sandy.value
// => test
sandy.value = “test2”;
// => ‘val is Changed to : test2’
sandy.value
// => “test2”

　除了__defineG/Setter__外, 你还可以使用’set’、’get’关键字在在原型对象上定义accessor,对于单个对象同样适用, 适用于Firefox 2.0+, Safari 3.0+, Google Chrome 1.0+ 和 Opera 9.5+.
复制代码 代码如下:
function Sandyval){
this.value = val;
}

Sandy.prototype = {
get value){
return this._value;
},
set valueval){
this._value = val;
}
};

//Or

var sandy = {
‘_value’ : ‘sandy’,
get value) {
　　return this._value;
},
set valueval) {
　　this._value = val;
}
}

最后一种方法,用到了Object的静态方法defineProperty,作用于单个对象,该方法应该属于ES5的范畴了,目前似乎只有Chrome 支持这种方法，其实Ie8也支持,但操作对象仅限于Dom节点Dom node),见IEBlog,该方法的使用见MDN.
复制代码 代码如下:
var sandy = {}, rValue;
Object.definePropertysandy, ‘value’ ,
{
‘set’ : functionval) {
rValue = val;
},
‘get’ : function) {
return rValue;
},
‘enumerable’ : true,
‘configurable’ : true
}
)
//Ie8+
Object.definePropertydocument.body, “description”, {
get : function ) {
return this.desc;
},
set : function val) {
this.desc = val;
}
});
document.body.description = “Content container”;
// document.body.description will now return “Content container”

‘enumerable’,’configuralbe’ 属于ES5规范中的Property Attributes属性特性),在这里就不做讨论了,有兴趣的Google或者直接去看ES5的文档. ^ ^