function Person()
{
this.username = new Array();
this.password = "123";
}
Person.prototype.getInfo = function()
{
alert(this.username + ", " + this.password);
}
var p = new Person();
var p2 = new Person();
p.username.push("zhangsan");
p2.username.push("lisi");
p.getInfo();
p2.getInfo();

function Person()
{
 this.username = new Array();
 this.password = "123";
}
Person.prototype={
 getInfo:function(){
 alert(this.username + ", " + this.password);
 }
}
var p = new Person();
var p2 = new Person();
p.username.push("zhangsan");
p2.username.push("lisi");
p.getInfo();
p2.getInfo();

Person.prototype={
a方法:function(){
 do somethings...
 },
b方法:function(){
 do somethings...
 }
}