# 2015年12月18日

## javascript

### 面向对象

```javascript
oDiv.onclick=function(){
    alert(this);
}
```

> 给一对象添加**事件**（click事件），等于给一个对象添加**方法**（function）；

**this**

* 当前发生事件的对象
* 当前的方法属于谁，this就是谁。

**对象的组成**

* 方法——函数：过程、动态的
* 属性——变量：状态、静态的

  **类与对象**

  类：模子 对象：产品

  var arr=new Array(1,2,3,4,5)

Array----- 类 arr ----- 对象

用构造函数加属性 用原型加方法

**继承**

```javascript
A.prototype.show=function ()
{
    alert(this.abc);
};
for(var i in A.prototype)
{
    B.prototype[i]=A.prototype[i];

}
B.prototype.fn=function(){
    alert('abc');
}
var objA=new A();
var objB=new B();

objA.fn();//error.
```

`call()`:可以改变函数`this`的指向。

```javascript
function A(){
    this.abc=12;
}

function B(){
    //这里的this指-->new B(),把A的this指向了B的this，本来给A加的属性，变成给B加的属性。
    A.call(this);
}
```


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