Function.prototype.addMethod = function(name,fn) {
    this[name] = fn;
    return this;
}
Function.prototype.addProtoMethod = function(name,fn) {
    this.prototype[name] = fn;
    return this;
}
var Method = function() {};

Method.addMethod('checkName',function() { return this;});
var testA = new Method();
Method.addProtoMethod('checkAge',function() {return this;});
var testB = new Method();
Method.addMethod('checkName',function() { return this.print();});
Function.prototype.print = function() {console.log('666');}
Method.checkName() //666

Method本身可以调用原型链上的addMethod(),他的实例不会有checkName()，checkName()属于类公有方法，checkAge()属于公有方法。

> Function.prototype.addMethod = function(name,fn) {
...     this[name] = fn;
...     return this;
... }
[Function]
> Function.prototype.addProtoMethod = function(name,fn) {
...     this.prototype[name] = fn;
...     return this;
... }
[Function]
>
> var Method = function() {};
undefined
> Method.addMethod('checkName',function() { return this.print();});
{ [Function] checkName: [Function] }
> Function.prototype.print = function() {console.log('666');}

for(var property in Method) {

... console.log(property);

... }

checkName

addMethod

addProtoMethod

print


Method.prototype.talk = function() {return false;}

[Function]

for(var property in Method) {

...     console.log(property); //

... }

checkName

addMethod

addProtoMethod

print

Method.test = function() {talk();}

[Function]

Method.test()

ReferenceError: talk is not defined

因为 Method 是Function 的实例，所以Function.prototype自定义添加的属性会显示。
而对Method.prototype而言，Method只是一个构造函数（类似合作关系），所以 talk()不会被找到。 （__proto__与prototype区别）