Javascript wrapper for cross domain requests.

gistfile1.txt

var XReq = function(params) {
	this.init(params);
	this.perform();
}

XReq.prototype = {
	'init': function(params) {
		var members = {
			'url':null,
			'error':function(xhr, error, message) {
				console.error([error, message]);
			},
			'success':function(data) {
				console.log(["No success handler for url " + that.url]);
			},
			'dataType':'text',
			'async':true,
			'data':{},
			'type':'GET',
			'xd':false
		};
		this._aborted = false;
		for (var i in members) { if (members.hasOwnProperty(i)) { 
			if (params[i] != undefined) { 
				this[i] = params[i];
			} else if (members[i] == null) {
				console.error("Parameter " + i + " is required");
			} else {
				this[i] = members[i];
			}
		}}
		if (this.url.match(CDN_DOMAIN)) {
			this.xd = true;
		}
		if (! window.XDomainRequest) {
			this.xd = false;
		}

		var that = this;
		if (this.xd) {  
			this.xr = new XDomainRequest();
		} else {
			this.xr = new XMLHttpRequest();
		}
	},
	'perform':function() {

		var query = '', send = '';
		var first = true;
		for (var i in this.data) { if (this.data.hasOwnProperty(i)) {
			query += (first?'':'&') + encodeURIComponent(i) +'='+encodeURIComponent(this.data[i]);
			first = false;
		}};

		if (this.type == 'GET') {
			if (query.length) { query = '?' + query; }
			this.xr.open(this.type, this.url+query, this.async);
		} else {
			this.xr.open(this.type, this.url, this.async);
			this.xr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
			this.xr.setRequestHeader("Content-length", this.data.length);
			this.xr.setRequestHeader("Connection", "close");
			send = query;
		}
		var that = this;
		this.xr.onerror = function() { that.error(that.xr, 'Could not load URL '+that.url, that.xr.responseText); };
		if (this.xd) {
			this.xr.onload = function() {
				that.on_success();
			}
		}
		this.xr.onreadystatechange = function() {
			var state = that.xr.readyState;
			if (state == 0 || that._aborted) {
				that.on_abort();
			} else if (state == 4) /** complete **/ {
				try {
					that.on_success();
				} catch (ex) {
					that.error(that.xr, 'error', ex);
				}
			}
			
		};
		try {
			this.xr.send(send);
		} catch (ex) {
			that.error(that.xr, "Error making request ("+that.url+")", that.xr.responseText);
		}
	},
	'on_abort':function() {
		this.error(this.xr, 'abort', '');
	},
	'on_success':function() {
		if (this.dataType == 'xml') { this.success(this.xr.responseXML); }
		else if (this.dataType == 'json') { 
			var text = this.xr.responseText;
			var json = !(/[^,:{}\[\]0-9.\-+Eaeflnr-u \n\r\t]/.test(text.replace(/"(\\.|[^"\\])*"/g, ''))) && eval('(' + text + ')');
			this.success(json);
		} else {
			this.success(this.xr.responseText);
		}

	},
	'abort' : function() { this._aborted = true; this.xr.abort(); }
}

As it stands, requires jquery to parse the responses.

added abort handling.