JavaScript 事件对象的实现

比如，我们定义了一个Classroom对象，这里我们定一个事件，当教室里的人增加超60人时就触发一个事件onFull;具体定义如下：

var Classroom=function() 
{ 
this.numberOfPeople=0; 
this.onFull=null; 
this.peopleEnter=function(number) 
{ 
this.numberOfPeople+=number; 
if(this.numberOfPeople>60&&this.onFull!=null) 
{ 
this.onFull(this.numberOfPeople); 
} 
} 
} 
function show1(number) 
{ 
alert("教室里有"+number+"人"); 
} 
function show2(number) 
{ 
alert("教室里超出了"+(number-60)+"人"); 
} 
var classroom1=new Classroom(); 
classroom1.onFull=show1; 
classroom1.peopleEnter(30); 
classroom1.peopleEnter(32); 
classroom1.onFull=show2; 
classroom1.peopleEnter(34);