API: ajax('url', callbackFunction?, postData?); --> returns: a handle object with an ".abort();" method for canceling the request.

simple-ajax

var ajax = (function( root ) {
  
	function getRequest() {
		if (root.ActiveXObject) return new ActiveXObject('Microsoft.XMLHTTP');
		else if (root.XMLHttpRequest) return new XMLHttpRequest();
		else return null;
	}
	
	return function(url, callback, post) {
		post = post || "";
		var req = getRequest();
		
		if (req) {
			
			req.onreadystatechange = function() {
				if (req.readyState == 4 && callback && typeof callback.call == 'function') {
					callback(req.responseText);
				}
			};

			if (post) {
				req.open("POST", url, true);
				req.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
				req.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
				req.setRequestHeader('Connection', 'close');
			} else {
				req.open("GET", url, true);
			}

			req.send(post);
		}
		
		return !req ? null : {
			abort: function() {
				req.onreadystatechange = undefined;
				req.abort && req.abort();
			}
		};
	};
	
}(this));