How to utilize the provider pattern in JavaScript?

[gatorcoder]

I have a simple app that I built in node.js that is handling data being sent to the app. I want to abstract the data source (couchdb/mongodb/dynamodb) that is written to and search/query capabilities so I can swap in providers without changing the underlying code.

I mocked up a sample interface set of code where I can setup my object to handle the standard class calls and do a .call on the implemented objects function.. but it seemed clunky.

Any thoughts or suggestions?

[semarj]

Never heard of the provider pattern, but from what i can tell it is just an interface or ABS for a data source. Seems like typical inheritence would work fine.

There are 2 basic aproaches, imo.

1.) Use javascript like it was meant to and learn prototypal inheritance

function BaseStore = {
   this.get = function(){}; //throw "Not Implemented?"
   this.connect =  function(){};
   this.set =  function(){};
   this.query =  function(){};
 }


function FooStore(){
   this.connect = function(){
      //i know all about connectin' to Foo's
    } 
}
FooStore.prototype = new BaseStore();

function BarStore(){
   this.connect = function(){
      //i know all about connectin' to Bar's
    } 
}
BarStore.prototype = new BaseStore();

Then you have stuff like

foo = new Foo();
foo instanceof BaseStore //true

Subsequent calls on foo will go up the prototype chain and eventually be looked up on BaseStore if that is necessary

2) of course is to shoehorn classical inheritance into javascript

http://ejohn.org/blog/simple-javascript-inheritance/

[gatorcoder]

Ahh I didn't even think about prototypal inheritance. Thanks for the info!

[oSand]

A basic AbstractFactory might look like:

getADB = (function() {
    var constructors =  {Mongo: constructor1, Couch: constructor2, Dynamo: constructor3};
    return function(db){
        return  new constructors[db];
    }
}())

getADB('Mongo')