DecoratorsClass.js

var verify1 = function(fn) {    
  return function() {       
    var args = $A(arguments);
    if($type(args[0]) != "string") 
    {
      throw new Error("First arg is not a string");       
    } 
    else  
    {          
      console.log("verify1 decorator run");
      return fn.apply(this, args);       
    }
  }
};  

var verify2 = function(fn) {    
  return function() { 
    var args = $A(arguments);
    if($type(args[1]) != "string")
    { 
      throw new Error("Second arg is not a string");
    }       
    else       
    {          
      console.log("verify2 decorator run")          
      return fn.apply(this, args);       
    }    
  } 
};


var generator = function(type) {
  return function(fn) {    
    return function() { 
      var args = $A(arguments);
      if($type(args[0]) != type)
      { 
        throw new Error("First arg is not a " + type);
      }       
      else       
      {          
        console.log("generator type checker run")          
        return fn.apply(this, args);       
      }    
    } 
  };
}


var MyClass = new Class({
  name: "MyClass",   
  aMethod: function(argA, argB) {     
    console.log("Hello from base class aMethod! argA " + argA + ", argB " + argB);     
    console.log(this.name);   
  }.decorate(verify2)
});  


var MySubClass = new Class({   
  Extends: MyClass,   
  name: "MySubClass",   
  aMethod: function(argA, argB) {
    console.log("before parent");     
    this.parent(argA, argB);     
    console.log("Hello from subclass aMethod! argA " + argA + ", argB " + argB);     
    console.log(this.name);   
  }.decorate(generator("object")) 
});  


var instance = new MySubClass(); 
instance.aMethod({}, "bar"); // works