如果要在之前写好的对象中添加新的静态方法或实例方法，要修改原有的对象结构，于是查看了jquery了extend方法，果然extend方法支持了jq的半边天，拿来主义，给自己的对象做扩张用。
下面进入正题： 
假如有以下一个对象 

var MyMath = { //加法 Add: <a class="tags" href="/tags/FUNCTION.html" title=function>function</a>(a, b){ return a + b; }, //减法 Sub: <a class="tags" href="/tags/FUNCTION.html" title=function>function</a>(a, b){ return a - b; } }  

对象名MyMath，有两个静态方法Add和Sub，正常调用： 

alert(MyMath.Add(3, 5)) //结果8  

好，现在如果现在MyMath增加两个静态方法（乘法、除法）怎么办，并且不要修改之前写好的对象，以前我们可以这么做： 

//新加一静态方法：Mul乘法 MyMath["Mul"] = <a class="tags" href="/tags/FUNCTION.html" title=function>function</a>(a, b){ return a * b; } //新加一静态方法：Div除法 MyMath["Div"] = <a class="tags" href="/tags/FUNCTION.html" title=function>function</a>(a, b){ return a / b; }  

这样，我们给MyMath添加两个方法：Mul和Div。正常调用：

alert(MyMath.Add(3, 5)) //结果8 alert(MyMath.Mul(3, 5)) //结果15  

但是，刚才增加方法的写法有点笨拙，每增加一个方法都要写一次对象名（MyMath），能不能想之前我们创建对象的时候那样，通过Json的结构去声明一个对象呢？ 
答案当然是可以了，通过模拟JQuery.extend函数，轻松做到。以下提取JQuery.extend函数并修改了函数名： 

MyMath.extend = <a class="tags" href="/tags/FUNCTION.html" title=function>function</a>(){ // copy <a class="tags" href="/tags/REFERENCE.html" title=reference>reference</a> to target <a class="tags" href="/tags/OBJECT.html" title=object>object</a> var target = arguments[0] || {}, i = 1, length = arguments.length, deep = false, options; // Handle a deep copy situation if (typeof target === "boolean") { deep = target; target = arguments[1] || {}; // skip the boolean and the target i = 2; } // Handle case when target is a string or something (possible in deep copy) if (typeof target !== "<a class="tags" href="/tags/OBJECT.html" title=object>object</a>" && !jQuery.isFunction(target)) target = {}; // extend jQuery itself if only one argument is passed if (length == i) { target = this; --i; } for (; i < length; i++) // Only deal with non-null/undefined values if ((options = arguments[i]) != null) // Extend the base <a class="tags" href="/tags/OBJECT.html" title=object>object</a> for (var name in options) { var src = target[name], copy = options[name]; // Prevent never-ending loop if (target === copy) continue; // Recurse if we're merging <a class="tags" href="/tags/OBJECT.html" title=object>object</a> values if (deep && copy && typeof copy === "<a class="tags" href="/tags/OBJECT.html" title=object>object</a>" && !copy.nodeType) target[name] = jQuery.extend(deep, // Never move original <a class="tags" href="/tags/OBJECT.html" title=object>object</a>s, clone them src || (copy.length != null ? [] : {}), copy); // Don't bring in undefined values else if (copy !== undefined) target[name] = copy; } // Return the modified <a class="tags" href="/tags/OBJECT.html" title=object>object</a> return target; };  

现在我们通过这个extend方法来增加刚才我们的方法（乘法、除法）： 

MyMath.extend({ Mul: <a class="tags" href="/tags/FUNCTION.html" title=function>function</a>(a, b){ return a * b; }, Div: <a class="tags" href="/tags/FUNCTION.html" title=function>function</a>(a, b){ return a / b; } });