자바스크립트 프로토타입에 대한 심층적인 탐색은 프로토타입 상속_자바스크립트 기술만큼 간단하지 않습니다.

<script>     
    function Point(x,y) 
    { 
        this.x = x; 
        this.y = y; 
    } 
    var p1 = new Point(1,2); 
    var p2 = new Point(3,4); 
    Point.prototype.z = 0; //动态为Point的原型添加了属性 
    alert(p1.z); 
    alert(p2.z);  //同时作用于Point类型创建的所有对象 
</script>

<script> 
function Point(x, y) 
{ 
    if(x) this.x = x; 
    if(y) this.y = y; 
} 
Point.prototype.x = 0; 
Point.prototype.y = 0; 
var p1 = new Point; 
var p2 = new Point(1,2); 
</script>

<script> 
function classA() 
{ 
    this.a = 100; 
    this.b = 200; 
    this.c = 300; 

    this.reset = function() 
    { 
        for(var each in this) 
        { 
            delete this[each]; 
        } 
    } 
} 
classA.prototype = new classA(); 

var a = new classA(); 
alert(a.a); 
a.a *= 2; 
a.b *= 2; 
a.c *= 2; 
alert(a.a); 
alert(a.b); 
alert(a.c); 
a.reset();   //调用reset方法将a的值恢复为默认值 
alert(a.a); 
alert(a.b); 
alert(a.c); 
</script>

<script> 
function Point(x, y) 
{ 
    if(x) this.x = x; 
    if(y) this.y = y; 
} 
Point.prototype.x = 0; 
Point.prototype.y = 0; 

function LineSegment(p1, p2) 
{ 
    //私有成员 
    var m_firstPoint = p1; 
    var m_lastPoint = p2; 
    var m_width = { 
        valueOf : function(){return Math.abs(p1.x - p2.x)}, 
        toString : function(){return Math.abs(p1.x - p2.x)} 
    } 
    var m_height = { 
        valueOf : function(){return Math.abs(p1.y - p2.y)}, 
        toString : function(){return Math.abs(p1.y - p2.y)} 
    } 
    //getter 
    this.getFirstPoint = function() 
    { 
        return m_firstPoint; 
    } 
    this.getLastPoint = function() 
    { 
        return m_lastPoint; 
    } 

    this.length = { 
        valueOf : function(){return Math.sqrt(m_width*m_width + m_height*m_height)}, 
        toString : function(){return Math.sqrt(m_width*m_width + m_height*m_height)} 
    } 
} 
var p1 = new Point; 
var p2 = new Point(2,3); 
var line1 = new LineSegment(p1, p2); 
var lp = line1.getFirstPoint(); 
lp.x = 100;  //不小心改写了lp的值，破坏了lp的原始值而且不可恢复 
alert(line1.getFirstPoint().x); 
alert(line1.length); //就连line1.lenght都发生了改变 
</script>

<script> 
function Point(x, y) 
{ 
    if(x) this.x = x; 
    if(y) this.y = y; 
} 
Point.prototype.x = 0; 
Point.prototype.y = 0; 

function LineSegment(p1, p2) 
{ 
    //私有成员 
    var m_firstPoint = p1; 
    var m_lastPoint = p2; 
    var m_width = { 
        valueOf : function(){return Math.abs(p1.x - p2.x)}, 
        toString : function(){return Math.abs(p1.x - p2.x)} 
    } 
    var m_height = { 
        valueOf : function(){return Math.abs(p1.y - p2.y)}, 
        toString : function(){return Math.abs(p1.y - p2.y)} 
    } 
    //getter 
    this.getFirstPoint = function() 
    { 
            function GETTER(){}; 
            GETTER.prototype = m_firstPoint; 
            return new GETTER(); 
    } 
    this.getLastPoint = function() 
    { 
            function GETTER(){}; 
            GETTER.prototype = m_lastPoint; 
            return new GETTER(); 
    } 

    this.length = { 
        valueOf : function(){return Math.sqrt(m_width*m_width + m_height*m_height)}, 
        toString : function(){return Math.sqrt(m_width*m_width + m_height*m_height)} 
    } 
} 
var p1 = new Point; 
var p2 = new Point(2,3); 
var line1 = new LineSegment(p1, p2); 
var lp = line1.getFirstPoint(); 
lp.x = 100;  //不小心改写了lp的值，但是没有破坏原始的值 
alert(line1.getFirstPoint().x); 
alert(line1.length); //line1.lenght不发生改变 
</script>

<script> 
function Polygon() 
{ 
    var m_points = []; 

    m_points = Array.apply(m_points, arguments); 

    function GETTER(){}; 
    GETTER.prototype = m_points[0]; 
    this.firstPoint = new GETTER(); 

    this.length = { 
        valueOf : function(){return m_points.length}, 
        toString : function(){return m_points.length} 
    } 

    this.add = function(){ 
        m_points.push.apply(m_points, arguments); 
    } 

    this.getPoint = function(idx) 
    { 
        return m_points[idx]; 
    } 

    this.setPoint = function(idx, point) 
    { 
        if(m_points[idx] == null) 
        { 
            m_points[idx] = point; 
        } 
        else 
        { 
            m_points[idx].x = point.x; 
            m_points[idx].y = point.y; 
        } 
    } 
} 
var p = new Polygon({x:1, y:2},{x:2, y:4},{x:2, y:6}); 
alert(p.length); 
alert(p.firstPoint.x); 
alert(p.firstPoint.y); 
p.firstPoint.x = 100; //不小心写了它的值 
alert(p.getPoint(0).x);  //不会影响到实际的私有成员 
delete p.firstPoint.x; //恢复 
alert(p.firstPoint.x); 

p.setPoint(0, {x:3,y:4}); //通过setter改写了实际的私有成员 
alert(p.firstPoint.x);  //getter的值发生了改变 
alert(p.getPoint(0).x); 
</script>

<script> 
var p1 = new Point(1,2); 
var points = []; 
var PointPrototype = function(){}; 
PointPrototype.prototype = p1; 
for(var i = 0; i < 10000; i++) 
{ 
        points[i] = new PointPrototype();  
        //由于PointPrototype的构造函数是空函数，因此它的构造要比直接构造//p1副本快得多。 
} 
</script>

<script> 
function ClassA() 
{ 
    this.a=[]; 
} 
function ClassB() 
{ 
    this.b=function(){}; 
} 
ClassB.prototype=new ClassA(); 
var objB1=new ClassB(); 
var objB2=new ClassB(); 
objB1.a.push(1,2,3); 
alert(objB2.a); 
//所有b的实例中的a成员全都变了！！这并不是这个例子所希望看到的。 
</script>