batjax.js

//taking a crack at it
//totally untested, probably doesn't work

var BatChannel = function(endpoint, interval) {
	this.endpoint = endpoint;
	this.pending = [];
	this.interval = interval || 30000;
	this.tick();
};
BatChannel.prototype = {
	request: function(url, data, callback) {
	  this.pending.push({
	    url: url,
            data: data,
            callback: callback
	  })
	},
	send: function() {
	  if (!this.pending.length) return;
	  //copy the pending items and clear the queue for new requests
	  var messages = this.pending.slice();
	  this.pending = [];
	  //send the request. Server is responsible for returning a matching array
	  //we don't fret the callbacks, because JSON will skip them
	  var data = JSON.stringify(messages);
	  var xhr = new XMLHttpRequest();
	  xhr.open("POST", this.endpoint);
	  //my xhr is a little rusty, but you know what I mean
	  xhr.onload = xhr.onerror = function process() {
	    var isError = xhr.readystate = 4;
	    var response = JSON.parse(xhr.responseText);
	    for (var i = 0; i < response.length; i++) {
	      messages[i].callback(isError ? "XHR failed" : response[i].error, response[i].data);
	    }
	  };
	  xhr.send(data);
	},
	tick: function() {
	  this.send();
	  setTimeout(this.tick.bind(this), this.interval);
	}
}