JayrockChannel.js

function JayrockChannel()
{
    this.rpc = function(call)
    {
        var async = typeof(call.callback) === 'function';
        var xhr = newXHR();
        xhr.open('POST', call.url, async, this.httpUserName, this.httpPassword);
        xhr.setRequestHeader('Content-Type', this.contentType || 'application/json; charset=utf-8');
        xhr.setRequestHeader('X-JSON-RPC', call.request.method);
        if (async) xhr.onreadystatechange = function() { xhr_onreadystatechange(xhr, call.callback); }
        xhr.send(JSON.stringify(call.request));
        call.handler = xhr;
        if (async) return call;
        if (xhr.status != 200) throw new Error(xhr.status + ' ' + xhr.statusText);
        var response = JSON.eval(xhr.responseText);
        if (response.error != null) throw response.error;
        return response.result;
    }

    function xhr_onreadystatechange(sender, callback)
    {
        if (sender.readyState == /* complete */ 4)
        {
            try {
                sender.onreadystatechange = null; // Avoid IE7 leak (bug #12964)
            }
            catch (e) {
                /* IE 6/Mobile throws for onreadystatechange = null */
            }

            var response = sender.status == 200 ?
                JSON.eval(sender.responseText) : {};

            callback(response, sender);
        }
    }

    function newXHR()
    {
        if (typeof(window) !== 'undefined' && window.XMLHttpRequest)
            return new XMLHttpRequest(); /* IE7, Safari 1.2, Mozilla 1.0/Firefox, and Netscape 7 */
        else
            return new ActiveXObject('Microsoft.XMLHTTP'); /* WSH and IE 5 to IE 6 */
    }
}