I have been working on creating a simple auxiliary class for sending requests using XmlHttpRequest. However, I am encountering some issues with the code. For instance, in Google Chrome, I am seeing the error message
INVALID_STATE_ERR: DOM Exception 11//@method XRequest: Object constructor. As this implements a singleton, the object can't be created by calling the constructor directly; GetInstance should be called instead
function XRequest() {
this.XHR = XRequest.CreateXHR();
}
XRequest.instance = null;
//@method static GetInstance: Creates a singleton object of type XRequest. This method should be called whenever an object of that type is required.
//@return: an instance of a XRequest object
XRequest.GetInstance = function() {
if(XRequest.instance == null) {
XRequest.instance = new XRequest();
}
return XRequest.instance;
}
//@method static CreateXHR: Implements a basic factory method for creating a XMLHttpRequest object
//@return: XMLHttp object or null
XRequest.CreateXHR = function() {
var xhr = null;
var factory = [
function() { return new XMLHttpRequest(); },
function() { return new ActiveXObject("Msxml2.XMLHTTP"); },
function() { return new ActiveXObject("Microsoft.XMLHTTP"); }
];
for(var i = 0; i < factory.length; ++i) {
var f = factory[i];
xhr = f();
if(xhr) return xhr;
}
return null;
}
XRequest.prototype.SetRequestHeader = function(name, value) {
if(this.XHR) {
this.XHR.setRequestHeader(name, value);
}
}
XRequest.prototype.SendRequest = function(args) {
var async = true;
var type = "";
var url = "";
var username = "";
var password = "";
var body = null;
var success = null;
var failure = null;
for(e in args) {
switch(e) {
case "async":
async = args[e];
break;
case "type":
type = args[e];
break;
case "success":
success = args[e];
break;
case "failure":
failure = args[e];
break;
case "url":
url = args[e];
break;
case "username":
username = args[e];
break;
case "password":
password = args[e];
break;
case "body":
body = args[e];
break;
case "setHeader":
var h = args[e].split(":");
if(h.length == 2) {
this.SetRequestHeader(h[0], h[1]);
}
break;
}
}
var that = this;
this.XHR.onreadystatechange = function() {
alert("readyState == " + that.XHR.readyState + " status == " + that.XHR.status);
if(that.XHR.readyState == 4) {
if(that.XHR.status == 200 || that.XHR.status == 0) {
if(success) success(that.XHR);
} else {
if(failure) failure();
}
}
};
this.XHR.open(type, url, async, username, password);
this.XHR.send(body);
}
Here's an example of how to use it:
<script language="javascript">
function onLoad() {
var x = XRequest.GetInstance();
x.SendRequest({type:"GET",
setHeader:"Accept:text/html, image/png, image/*, */*",
url: "http://your_server.com/getData?param1=test",
success:onSuccess, failure:onFail
});
}
function onSuccess(obj) {
alert("OK");
}
function onFail() {
alert("Not at this time!");
}
</script>