Javascript的简单继承

 function First(age, name) {
this.age = age;
this.name = name;
}
First.prototype.getAge = function() {
return this.age;
};
First.prototype.toString = function() {
return "[ age: " + this.age + ", name: " + this.name + " ]";
};

function Second(age, name, password) {
First.call(this, age, name);
this.password = password;
}
Second.prototype = new First();
Second.prototype.constructor = Second;
Second.prototype.getPassword = function() {
return this.password;
};
Second.prototype.toString = function() {
return "[ age: " + this.age + ", name: " + this.name + ", password: " + this.password + " ]";
};
//由于通过Second.prototype = new First();
//继承了父类First的name和age属性，需要通过子类显示删除两个属性
delete Second.prototype.age;
delete Second.prototype.name;

//继承First
function Second2(age, name, sex) {
First.call(this, age, name);
this.sex = sex;
}
Second2.prototype.toString = function() {
return "[ age: " + this.age + ", name: " + this.name + ", sex: " + this.sex + " ]";
};
Second2.prototype.getSex = function() {
return this.sex;
};

function Third(age, name, password, address, email, sex) {
Second.call(this, age, name, password);
Second2.call(this, age, name, sex);
this.address = address;
this.email = email;
}
Third.prototype = new Second();
Third.prototype.constructor = Third;
Third.prototype.getAddress = function() {
return this.address;
};
Third.prototype.setEmail = function(email) {
this.email = email;
};
Third.prototype.toString = function() {
return "[ age: " + this.age + ", name: " + this.name + ", password: " + this.password + ", address: " + this.address + ", email: " + this.email + " ]";
};
delete Third.prototype.name;
delete Third.prototype.age;
delete Third.prototype.password;