Is this a good decorator pattern for javascript?
- by Kucebe
I need some simple objects that could become more complex later, with many different properties, so i thought to decorator pattern.
I made this looking at Crockford's power constructor and object augmentation:
//add property to object
Object.prototype.addProperty = function(name, func){
for(propertyName in this){
if(propertyName == name){
throw new Error(propertyName + " is already defined");
}
}
this[name] = func;
};
//constructor of base object
var BaseConstructor = function(param){
var _privateVar = param;
return{
getPrivateVar: function(){
return _privateVar;
}
};
};
//a simple decorator, adds one private attribute and one privileged method
var simpleDecorator = function(obj, param){
var _privateVar = param;
var privilegedMethod1 = function(){
return "privateVar of decorator is: " + _privateVar;
};
obj.addProperty("privilegedMethod1", privilegedMethod1);
return obj;
}
//a more complex decorator, adds public and private properties
var complexDecorator = function(obj, param1, param2){
//private properties
var _privateVar = param1;
var _privateMethod = function(x){
for(var i=0; i<x; i++){
_privateVar += x;
}
return _privateVar;
};
//public properties
var publicVar = "I'm public";
obj.addProperty("publicVar", publicVar);
var privilegedMethod2 = function(){
return _privateMethod(param2);
};
obj.addProperty("privilegedMethod2", privilegedMethod2);
var publicMethod = function(){
var temp = this.privilegedMethod2();
return "do something: " + temp + " - publicVar is: " + this.publicVar;
};
obj.addProperty("publicMethod", publicMethod);
return obj;
}
//new basic object
var myObj = BaseConstructor("obj1");
//the basic object will be decorated
var myObj = simpleDecorator(obj, "aParam");
//the basic object will be decorated with other properties
var myObj = complexDecorator(obj, 2, 3);
Is this a good way to have Decorator Pattern in javascript?
Are there other better ways to do this?
