Micro Promise implementation

promise.js

dojox.Promise = function(){
	
	return {
		emit: function(data){ // stub function
		},
		 
		then: function(doneHandler,errHandler){
			var promise = new dojox.Promise();
			dojo.connect(this, 'emit', function(data){
				if(doneHandler && !(data instanceof Error)){
					var res = doneHandler(data);
					promise.emit(res);
				}
				if(errHandler && (data instanceof Error)){
					errHandler(data);
					promise.emit(data);
				}
			});
			return promise;
		}
	}
};