Javascript jQuery JSON polling

poller.js

function Poller (url, callback) {
	this.url = url;
	this.callback = callback;

	this.start = function(interval) {
		var url = this.url;
		var callback = this.callback;
		
		var fn = function() {
			jQuery.getJSON(url, callback);
		};
		
		fn();
		this.interval = self.setInterval(fn, interval);
	};

	this.stop = function() {
		if (this.interval) {
			self.clearInterval(this.interval);
		}
	};
};