javaScript的类型函数（如Number/String/Boolean/Array/Date/Obejct等）都是继承于 Function.prototype，所以给Function.prototype增加方法，同时也会影响到由它衍生的下层类型函数。如：

Function.prototype.addMethod=function(methodName,func){   if(!this[methodName]){    this[methodName]=func;//给类型增加方法，类似于类型的静态方法。func方法是赋于了类型而非实例。   }   return this;//this 将绑定到方法的调用对象(类型函数),返回this可以进行链式调用  }    Array.addMethod('testFun',function(){alert(this)});  //Array.testFun();  //function Array() {[native code]}  Object.addMethod('testFun',function(){alert(this)});  //Object.testFun();  //function Object() {[native code]}  Boolean.addMethod('testFun',function(){alert(this)});  //Boolean.testFun();  //function Boolean() {[native code]}    function CustomObject(name,value){   this.name=name || 'CustomObject';   this.value=value || 0;   this.toString=function(){return '[name:'+this.name+',value:'+this.value+']'}  }  CustomObject.addMethod('testFun',function(){alert(this)});  /* return:   * function CustomObject(name, value) {      this.name = name || "CustomObject";      this.value = value || 0;      this.toString = function () {return "[name:" + this.name + ",value:" + this.value + "]";};  }   */  CustomObject.testFun();

 

此时如果用实例来调用的话，则会报错。如：

var customObject=new CustomObject(); //定义一个CustomObject实例  customObject.testFun();//Error: temp.testFun is not a function

 

给实例增加方法

如果给类型实例增加方法，则应该把方法绑定到类型的prototype上。如

Function.prototype.addMethod=function(methodName,func){   if(!this.prototype[methodName]){    this.prototype[methodName]=func;//给原型增加方法，此方法会影响到该类型的实例上   }   return this.prototype;//返回原型，此类型实例可以进行链形调用  }    Object.addMethod('testFun',function(){alert(this)});  //({toString:function(){return '[Empty Object]'}}).testFun();   //[Empty Object]  Number.addMethod('testFun',function(){alert(this)});  //(5).testFun();    //5  String.addMethod('testFun',function(){alert(this)});  //'test'.testFun();    //'test'  Boolean.addMethod('testFun',function(){alert(this)});  //true.testFun();    //true  Array.addMethod('testFun',function(){alert(this)});  //(['a','b']).testFun();    //a,b  Date.addMethod('testFun',function(){alert(this)});  //new Date().testFun();    //Tue Dec 27 2011 11:20:58 GMT-0800 (Pacific Standard Time)      function CustomObject(name,value){   this.name=name || 'CustomObject';   this.value=value || 0;   this.toString=function(){return '[name:'+this.name+',value:'+this.value+']'}  }  CustomObject.addMethod('testFun',function(){alert(this)});  var customObject=new CustomObject();   customObject.testFun();   //[name:CustomObject,value:0]

 

若此时用类型调用testFun,则会报错。如

Array.addMethod('testFun',function(){alert(this)});  //Array.testFun();     //Error: Array.testFun is not a function  CustomObject.addMethod('testFun',function(){alert(this)});  CustomObject.testFun();  //Error: CustomObject.testFun is not a function