妙用缓存调用链实现JS方法的重载

var seven={
  dosomething:function(){
    switch(arguments.length){
      case 0:
        console.log(arguments.length);
        //dosomething
        break;
      case 1:
        console.log(arguments.length);
        //dosomething
        break;
       case 2:
        //dosomething
        console.log(arguments.length);
        break;
    }
  }
}

var seven = {
  addMethod: function (fname, func) {
    var old = this[fname];
    this[fname] = function () {
      if (arguments.length == func.length) {
        return func.apply(this,arguments);
      }
      if (typeof old == 'function') {
        return old.apply(this, arguments);
      }
    }
  }
};

seven.addMethod('dosomething', function (x) {
  console.log(arguments.length);
   //dosomething
});
seven.addMethod('dosomething', function (x,y) {
  console.log(arguments.length);
   //dosomething
});
seven.addMethod('dosomething', function (x,y,z) {
  console.log(arguments.length);
   //dosomething
});