Javascript 面向对象编程(coolshell)(4)

function Person(name, email, website){
this.name = name;
this.email = email;
this.website = website;
};

Person.prototype.sayHello = function(){
var hello = "Hello, I am "+ this.name + ", <br>" +
"my email is: " + this.email + ", <br>" +
"my website is: " + this.website;
return hello;
};

function Student(name, email, website, no, dept){
var proto = Object.getPrototypeOf;
proto(Student.prototype).constructor.call(this, name, email, website);
this.no = no;
this.dept = dept;
}

// 继承prototype
Student.prototype = Object.create(Person.prototype);

//重置构造函数
Student.prototype.constructor = Student;

//重载sayHello()
Student.prototype.sayHello = function(){
var proto = Object.getPrototypeOf;
var hello = proto(Student.prototype).sayHello.call(this) + '<br>';
hello += "my student no is: " + this. no + ", <br>" +
"my departent is: " + this. dept;
return hello;
};

var me = new Student(
"Chen Hao",
"haoel@hotmail.com",
"http://jb51.net",
"12345678",
"Computer Science"
);
document.write(me.sayHello());

兼容性
上面的这些代码并不一定能在所有的浏览器下都能运行，因为上面这些代码遵循 ECMAScript 5 的规范，关于ECMAScript 5 的浏览器兼容列表，你可以看这里“ES5浏览器兼容表”。

本文中的所有代码都在Chrome最新版中测试过了。

下面是一些函数，可以用在不兼容ES5的浏览器中：

Object.create()函数

复制代码 代码如下:

function clone(proto) {
function Dummy() { }

Dummy.prototype = proto;
Dummy.prototype.constructor = Dummy;

return new Dummy(); //等价于Object.create(Person);
}

var me = clone(Person);

defineProperty()函数

复制代码 代码如下:

function defineProperty(target, key, descriptor) {
if (descriptor.value){
target[key] = descriptor.value;
}else {
descriptor.get && target.__defineGetter__(key, descriptor.get);
descriptor.set && target.__defineSetter__(key, descriptor.set);
}

return target
}

keys()函数

复制代码 代码如下:

function keys(object) { var result, key
result = [];
for (key in object){
if (object.hasOwnProperty(key)) result.push(key)
}

return result;
}

Object.getPrototypeOf() 函数

复制代码 代码如下:

function proto(object) {
return !object? null
: '__proto__' in object? object.__proto__
: /* not exposed? */ object.constructor.prototype
}

bind 函数

复制代码 代码如下:

var slice = [].slice

function bind(fn, bound_this) { var bound_args
bound_args = slice.call(arguments, 2)
return function() { var args
args = bound_args.concat(slice.call(arguments))
return fn.apply(bound_this, args) }
}

参考
W3CSchool
MDN (Mozilla Developer Network)
MSDN (Microsoft Software Development Network)

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