API: connection connection_core.js (YUI Library)

# Yahoo! UI Library

### connection 2.9.0

Yahoo! UI Library > connection > connection_core.js (source view)
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    /**
     * The Connection Manager provides a simplified interface to the XMLHttpRequest
     * object.  It handles cross-browser instantiantion of XMLHttpRequest, negotiates the
     * interactive states and server response, returning the results to a pre-defined
     * callback you create.
     *
     * @namespace YAHOO.util
     * @module connection
     * @requires yahoo
     * @requires event
     */

    /**
     * The Connection Manager singleton provides methods for creating and managing
     * asynchronous transactions.
     *
     * @class YAHOO.util.Connect
     */

    YAHOO.util.Connect =
    {
      /**
       * @description Array of MSFT ActiveX ids for XMLHttpRequest.
       * @property _msxml_progid
       * @private
       * @static
       * @type array
       */
        _msxml_progid:[
            'Microsoft.XMLHTTP',
            'MSXML2.XMLHTTP.3.0',
            'MSXML2.XMLHTTP'
            ],

      /**
       * @description Object literal of HTTP header(s)
       * @property _http_header
       * @private
       * @static
       * @type object
       */
        _http_headers:{},

      /**
       * @description Determines if HTTP headers are set.
       * @property _has_http_headers
       * @private
       * @static
       * @type boolean
       */
        _has_http_headers:false,

     /**
      * @description Determines if a default header of
      * Content-Type of 'application/x-www-form-urlencoded'
      * will be added to any client HTTP headers sent for POST
      * transactions.
      * @property _use_default_post_header
      * @private
      * @static
      * @type boolean
      */
        _use_default_post_header:true,

     /**
      * @description The default header used for POST transactions.
      * @property _default_post_header
      * @private
      * @static
      * @type boolean
      */
        _default_post_header:'application/x-www-form-urlencoded; charset=UTF-8',

     /**
      * @description The default header used for transactions involving the
      * use of HTML forms.
      * @property _default_form_header
      * @private
      * @static
      * @type boolean
      */
        _default_form_header:'application/x-www-form-urlencoded',

     /**
      * @description Determines if a default header of
      * 'X-Requested-With: XMLHttpRequest'
      * will be added to each transaction.
      * @property _use_default_xhr_header
      * @private
      * @static
      * @type boolean
      */
        _use_default_xhr_header:true,

     /**
      * @description The default header value for the label
      * "X-Requested-With".  This is sent with each
      * transaction, by default, to identify the
      * request as being made by YUI Connection Manager.
      * @property _default_xhr_header
      * @private
      * @static
      * @type boolean
      */
        _default_xhr_header:'XMLHttpRequest',

     /**
      * @description Determines if custom, default headers
      * are set for each transaction.
      * @property _has_default_header
      * @private
      * @static
      * @type boolean
      */
        _has_default_headers:true,

     /**
       * @description Property modified by setForm() to determine if the data
       * should be submitted as an HTML form.
       * @property _isFormSubmit
       * @private
       * @static
       * @type boolean
       */
    	_isFormSubmit:false,

     /**
      * @description Determines if custom, default headers
      * are set for each transaction.
      * @property _has_default_header
      * @private
      * @static
      * @type boolean
      */
        _default_headers:{},

     /**
      * @description Collection of polling references to the polling mechanism in handleReadyState.
      * @property _poll
      * @private
      * @static
      * @type object
      */
        _poll:{},

     /**
      * @description Queue of timeout values for each transaction callback with a defined timeout value.
      * @property _timeOut
      * @private
      * @static
      * @type object
      */
        _timeOut:{},

      /**
       * @description The polling frequency, in milliseconds, for HandleReadyState.
       * when attempting to determine a transaction's XHR readyState.
       * The default is 50 milliseconds.
       * @property _polling_interval
       * @private
       * @static
       * @type int
       */
         _polling_interval:50,

      /**
       * @description A transaction counter that increments the transaction id for each transaction.
       * @property _transaction_id
       * @private
       * @static
       * @type int
       */
         _transaction_id:0,

      /**
       * @description Custom event that fires at the start of a transaction
       * @property startEvent
       * @private
       * @static
       * @type CustomEvent
       */
        startEvent: new YAHOO.util.CustomEvent('start'),

      /**
       * @description Custom event that fires when a transaction response has completed.
       * @property completeEvent
       * @private
       * @static
       * @type CustomEvent
       */
        completeEvent: new YAHOO.util.CustomEvent('complete'),

      /**
       * @description Custom event that fires when handleTransactionResponse() determines a
       * response in the HTTP 2xx range.
       * @property successEvent
       * @private
       * @static
       * @type CustomEvent
       */
        successEvent: new YAHOO.util.CustomEvent('success'),

      /**
       * @description Custom event that fires when handleTransactionResponse() determines a
       * response in the HTTP 4xx/5xx range.
       * @property failureEvent
       * @private
       * @static
       * @type CustomEvent
       */
        failureEvent: new YAHOO.util.CustomEvent('failure'),

      /**
       * @description Custom event that fires when a transaction is successfully aborted.
       * @property abortEvent
       * @private
       * @static
       * @type CustomEvent
       */
        abortEvent: new YAHOO.util.CustomEvent('abort'),

      /**
       * @description A reference table that maps callback custom events members to its specific
       * event name.
       * @property _customEvents
       * @private
       * @static
       * @type object
       */
        _customEvents:
        {
            onStart:['startEvent', 'start'],
            onComplete:['completeEvent', 'complete'],
            onSuccess:['successEvent', 'success'],
            onFailure:['failureEvent', 'failure'],
            onUpload:['uploadEvent', 'upload'],
            onAbort:['abortEvent', 'abort']
        },

      /**
       * @description Member to add an ActiveX id to the existing xml_progid array.
       * In the event(unlikely) a new ActiveX id is introduced, it can be added
       * without internal code modifications.
       * @method setProgId
       * @public
       * @static
       * @param {string} id The ActiveX id to be added to initialize the XHR object.
       * @return void
       */
        setProgId:function(id)
        {
            this._msxml_progid.unshift(id);
            YAHOO.log('ActiveX Program Id  ' + id + ' added to _msxml_progid.', 'info', 'Connection');
        },

      /**
       * @description Member to override the default POST header.
       * @method setDefaultPostHeader
       * @public
       * @static
       * @param {boolean} b Set and use default header - true or false .
       * @return void
       */
        setDefaultPostHeader:function(b)
        {
            if(typeof b == 'string'){
                this._default_post_header = b;
    			this._use_default_post_header = true;

                YAHOO.log('Default POST header set to  ' + b, 'info', 'Connection');
            }
            else if(typeof b == 'boolean'){
                this._use_default_post_header = b;
            }
        },

      /**
       * @description Member to override the default transaction header..
       * @method setDefaultXhrHeader
       * @public
       * @static
       * @param {boolean} b Set and use default header - true or false .
       * @return void
       */
        setDefaultXhrHeader:function(b)
        {
            if(typeof b == 'string'){
                this._default_xhr_header = b;
                YAHOO.log('Default XHR header set to  ' + b, 'info', 'Connection');
            }
            else{
                this._use_default_xhr_header = b;
            }
        },

      /**
       * @description Member to modify the default polling interval.
       * @method setPollingInterval
       * @public
       * @static
       * @param {int} i The polling interval in milliseconds.
       * @return void
       */
        setPollingInterval:function(i)
        {
            if(typeof i == 'number' && isFinite(i)){
                this._polling_interval = i;
                YAHOO.log('Default polling interval set to ' + i +'ms', 'info', 'Connection');
            }
        },

      /**
       * @description Instantiates a XMLHttpRequest object and returns an object with two properties:
       * the XMLHttpRequest instance and the transaction id.
       * @method createXhrObject
       * @private
       * @static
       * @param {int} transactionId Property containing the transaction id for this transaction.
       * @return object
       */
        createXhrObject:function(transactionId)
        {
            var obj,http,i;
            try
            {
                // Instantiates XMLHttpRequest in non-IE browsers and assigns to http.
                http = new XMLHttpRequest();
                //  Object literal with http and tId properties
                obj = { conn:http, tId:transactionId, xhr: true };
                YAHOO.log('XHR object created for transaction ' + transactionId, 'info', 'Connection');
            }
            catch(e)
            {
                for(i=0; i<this._msxml_progid.length; ++i){
                    try
                    {
                        // Instantiates XMLHttpRequest for IE and assign to http
                        http = new ActiveXObject(this._msxml_progid[i]);
                        //  Object literal with conn and tId properties
                        obj = { conn:http, tId:transactionId, xhr: true };
                        YAHOO.log('ActiveX XHR object created for transaction ' + transactionId, 'info', 'Connection');
                        break;
                    }
                    catch(e1){}
                }
            }
            finally
            {
                return obj;
            }
        },

      /**
       * @description This method is called by asyncRequest to create a
       * valid connection object for the transaction.  It also passes a
       * transaction id and increments the transaction id counter.
       * @method getConnectionObject
       * @private
       * @static
       * @return {object}
       */
        getConnectionObject:function(t)
        {
            var o, tId = this._transaction_id;

            try
            {
                if(!t){
                    o = this.createXhrObject(tId);
                }
                else{
                    o = {tId:tId};
                    if(t==='xdr'){
                        o.conn = this._transport;
                        o.xdr = true;
                    }
                    else if(t==='upload'){
                        o.upload = true;
                    }
                }

                if(o){
                    this._transaction_id++;
                }
            }
            catch(e){}
            return o;
        },

      /**
       * @description Method for initiating an asynchronous request via the XHR object.
       * @method asyncRequest
       * @public
       * @static
       * @param {string} method HTTP transaction method
       * @param {string} uri Fully qualified path of resource
       * @param {callback} callback User-defined callback function or object
       * @param {string} postData POST body
       * @return {object} Returns the connection object
       */
        asyncRequest:function(method, uri, callback, postData)
        {
            var args = callback&&callback.argument?callback.argument:null,
                YCM = this,
                o, t;

            if(this._isFileUpload){
                t = 'upload';
            }
            else if(callback && callback.xdr){
                t = 'xdr';
            }

            o = this.getConnectionObject(t);
            if(!o){
                YAHOO.log('Unable to create connection object.', 'error', 'Connection');
                return null;
            }
            else{

                // Intialize any transaction-specific custom events, if provided.
                if(callback && callback.customevents){
                    this.initCustomEvents(o, callback);
                }

                if(this._isFormSubmit){
                    if(this._isFileUpload){
                        window.setTimeout(function(){YCM.uploadFile(o, callback, uri, postData);}, 10);
                        return o;
                    }

                    // If the specified HTTP method is GET, setForm() will return an
                    // encoded string that is concatenated to the uri to
                    // create a querystring.
                    if(method.toUpperCase() == 'GET'){
                        if(this._sFormData.length !== 0){
                            // If the URI already contains a querystring, append an ampersand
                            // and then concatenate _sFormData to the URI.
                            uri += ((uri.indexOf('?') == -1)?'?':'&') + this._sFormData;
                        }
                    }
                    else if(method.toUpperCase() == 'POST'){
                        // If POST data exist in addition to the HTML form data,
                        // it will be concatenated to the form data.
                        postData = postData?this._sFormData + "&" + postData:this._sFormData;
                    }
                }

                if(method.toUpperCase() == 'GET' && (callback && callback.cache === false)){
                    // If callback.cache is defined and set to false, a
                    // timestamp value will be added to the querystring.
                    uri += ((uri.indexOf('?') == -1)?'?':'&') + "rnd=" + new Date().valueOf().toString();
                }

                // Each transaction will automatically include a custom header of
                // "X-Requested-With: XMLHttpRequest" to identify the request as
                // having originated from Connection Manager.
                if(this._use_default_xhr_header){
                    if(!this._default_headers['X-Requested-With']){
                        this.initHeader('X-Requested-With', this._default_xhr_header, true);
                        YAHOO.log('Initialize transaction header X-Request-Header to XMLHttpRequest.', 'info', 'Connection');
                    }
                }

                //If the transaction method is POST and the POST header value is set to true
                //or a custom value, initalize the Content-Type header to this value.
                if((method.toUpperCase() === 'POST' && this._use_default_post_header) && this._isFormSubmit === false){
                    this.initHeader('Content-Type', this._default_post_header);
                    YAHOO.log('Initialize header Content-Type to application/x-www-form-urlencoded; UTF-8 for POST transaction.', 'info', 'Connection');
                }

                if(o.xdr){
                    this.xdr(o, method, uri, callback, postData);
                    return o;
                }

                o.conn.open(method, uri, true);
                //Initialize all default and custom HTTP headers,
                if(this._has_default_headers || this._has_http_headers){
                    this.setHeader(o);
                }

                this.handleReadyState(o, callback);
                o.conn.send(postData || '');
                YAHOO.log('Transaction ' + o.tId + ' sent.', 'info', 'Connection');

                // Reset the HTML form data and state properties as
                // soon as the data are submitted.
                if(this._isFormSubmit === true){
                    this.resetFormState();
                }

                // Fire global custom event -- startEvent
                this.startEvent.fire(o, args);

                if(o.startEvent){
                    // Fire transaction custom event -- startEvent
                    o.startEvent.fire(o, args);
                }

                return o;
            }
        },

      /**
       * @description This method creates and subscribes custom events,
       * specific to each transaction
       * @method initCustomEvents
       * @private
       * @static
       * @param {object} o The connection object
       * @param {callback} callback The user-defined callback object
       * @return {void}
       */
        initCustomEvents:function(o, callback)
        {
            var prop;
            // Enumerate through callback.customevents members and bind/subscribe
            // events that match in the _customEvents table.
            for(prop in callback.customevents){
                if(this._customEvents[prop][0]){
                    // Create the custom event
                    o[this._customEvents[prop][0]] = new YAHOO.util.CustomEvent(this._customEvents[prop][1], (callback.scope)?callback.scope:null);
                    YAHOO.log('Transaction-specific Custom Event ' + o[this._customEvents[prop][1]] + ' created.', 'info', 'Connection');

                    // Subscribe the custom event
                    o[this._customEvents[prop][0]].subscribe(callback.customevents[prop]);
                    YAHOO.log('Transaction-specific Custom Event ' + o[this._customEvents[prop][1]] + ' subscribed.', 'info', 'Connection');
                }
            }
        },

      /**
       * @description This method serves as a timer that polls the XHR object's readyState
       * property during a transaction, instead of binding a callback to the
       * onreadystatechange event.  Upon readyState 4, handleTransactionResponse
       * will process the response, and the timer will be cleared.
       * @method handleReadyState
       * @private
       * @static
       * @param {object} o The connection object
       * @param {callback} callback The user-defined callback object
       * @return {void}
       */

        handleReadyState:function(o, callback)

        {
            var oConn = this,
                args = (callback && callback.argument)?callback.argument:null;

            if(callback && callback.timeout){
                this._timeOut[o.tId] = window.setTimeout(function(){ oConn.abort(o, callback, true); }, callback.timeout);
            }

            this._poll[o.tId] = window.setInterval(
                function(){
                    if(o.conn && o.conn.readyState === 4){

                        // Clear the polling interval for the transaction
                        // and remove the reference from _poll.
                        window.clearInterval(oConn._poll[o.tId]);
                        delete oConn._poll[o.tId];

                        if(callback && callback.timeout){
                            window.clearTimeout(oConn._timeOut[o.tId]);
                            delete oConn._timeOut[o.tId];
                        }

                        // Fire global custom event -- completeEvent
                        oConn.completeEvent.fire(o, args);

                        if(o.completeEvent){
                            // Fire transaction custom event -- completeEvent
                            o.completeEvent.fire(o, args);
                        }

                        oConn.handleTransactionResponse(o, callback);
                    }
                }
            ,this._polling_interval);
        },

      /**
       * @description This method attempts to interpret the server response and
       * determine whether the transaction was successful, or if an error or
       * exception was encountered.
       * @method handleTransactionResponse
       * @private
       * @static
       * @param {object} o The connection object
       * @param {object} callback The user-defined callback object
       * @param {boolean} isAbort Determines if the transaction was terminated via abort().
       * @return {void}
       */
        handleTransactionResponse:function(o, callback, isAbort)
        {
            var httpStatus, responseObject,
                args = (callback && callback.argument)?callback.argument:null,
                xdrS = (o.r && o.r.statusText === 'xdr:success')?true:false,
                xdrF = (o.r && o.r.statusText === 'xdr:failure')?true:false,
                xdrA = isAbort;

            try
            {
                if((o.conn.status !== undefined && o.conn.status !== 0) || xdrS){
                    // XDR requests will not have HTTP status defined. The
                    // statusText property will define the response status
                    // set by the Flash transport.
                    httpStatus = o.conn.status;
                }
                else if(xdrF && !xdrA){
                    // Set XDR transaction failure to a status of 0, which
                    // resolves as an HTTP failure, instead of an exception.
                    httpStatus = 0;
                }
                else{
                    httpStatus = 13030;
                }
            }
            catch(e){

                 // 13030 is a custom code to indicate the condition -- in Mozilla/FF --
                 // when the XHR object's status and statusText properties are
                 // unavailable, and a query attempt throws an exception.
                httpStatus = 13030;
            }

            if((httpStatus >= 200 && httpStatus < 300) || httpStatus === 1223 || xdrS){
                responseObject = o.xdr ? o.r : this.createResponseObject(o, args);
                if(callback && callback.success){
                    if(!callback.scope){
                        callback.success(responseObject);
                        YAHOO.log('Success callback. HTTP code is ' + httpStatus, 'info', 'Connection');
                    }
                    else{
                        // If a scope property is defined, the callback will be fired from
                        // the context of the object.
                        callback.success.apply(callback.scope, [responseObject]);
                        YAHOO.log('Success callback with scope. HTTP code is ' + httpStatus, 'info', 'Connection');
                    }
                }

                // Fire global custom event -- successEvent
                this.successEvent.fire(responseObject);

                if(o.successEvent){
                    // Fire transaction custom event -- successEvent
                    o.successEvent.fire(responseObject);
                }
            }
            else{
                switch(httpStatus){
                    // The following cases are wininet.dll error codes that may be encountered.
                    case 12002: // Server timeout
                    case 12029: // 12029 to 12031 correspond to dropped connections.
                    case 12030:
                    case 12031:
                    case 12152: // Connection closed by server.
                    case 13030: // See above comments for variable status.
                        // XDR transactions will not resolve to this case, since the
                        // response object is already built in the xdr response.
                        responseObject = this.createExceptionObject(o.tId, args, (isAbort?isAbort:false));
                        if(callback && callback.failure){
                            if(!callback.scope){
                                callback.failure(responseObject);
                                YAHOO.log('Failure callback. Exception detected. Status code is ' + httpStatus, 'warn', 'Connection');
                            }
                            else{
                                callback.failure.apply(callback.scope, [responseObject]);
                                YAHOO.log('Failure callback with scope. Exception detected. Status code is ' + httpStatus, 'warn', 'Connection');
                            }
                        }

                        break;
                    default:
                        responseObject = (o.xdr) ? o.response : this.createResponseObject(o, args);
                        if(callback && callback.failure){
                            if(!callback.scope){
                                callback.failure(responseObject);
                                YAHOO.log('Failure callback. HTTP status code is ' + httpStatus, 'warn', 'Connection');
                            }
                            else{
                                callback.failure.apply(callback.scope, [responseObject]);
                                YAHOO.log('Failure callback with scope. HTTP status code is ' + httpStatus, 'warn', 'Connection');
                            }
                        }
                }

                // Fire global custom event -- failureEvent
                this.failureEvent.fire(responseObject);

                if(o.failureEvent){
                    // Fire transaction custom event -- failureEvent
                    o.failureEvent.fire(responseObject);
                }

            }

            this.releaseObject(o);
            responseObject = null;
        },

      /**
       * @description This method evaluates the server response, creates and returns the results via
       * its properties.  Success and failure cases will differ in the response
       * object's property values.
       * @method createResponseObject
       * @private
       * @static
       * @param {object} o The connection object
       * @param {callbackArg} callbackArg The user-defined argument or arguments to be passed to the callback
       * @return {object}
       */
        createResponseObject:function(o, callbackArg)
        {
            var obj = {}, headerObj = {},
                i, headerStr, header, delimitPos;

            try
            {
                headerStr = o.conn.getAllResponseHeaders();
                header = headerStr.split('\n');
                for(i=0; i<header.length; i++){
                    delimitPos = header[i].indexOf(':');
                    if(delimitPos != -1){
                        headerObj[header[i].substring(0,delimitPos)] = YAHOO.lang.trim(header[i].substring(delimitPos+2));
                    }
                }
            }
            catch(e){}

            obj.tId = o.tId;
            // Normalize IE's response to HTTP 204 when Win error 1223.
            obj.status = (o.conn.status == 1223)?204:o.conn.status;
            // Normalize IE's statusText to "No Content" instead of "Unknown".
            obj.statusText = (o.conn.status == 1223)?"No Content":o.conn.statusText;
            obj.getResponseHeader = headerObj;
            obj.getAllResponseHeaders = headerStr;
            obj.responseText = o.conn.responseText;
            obj.responseXML = o.conn.responseXML;

            if(callbackArg){
                obj.argument = callbackArg;
            }

            return obj;
        },

      /**
       * @description If a transaction cannot be completed due to dropped or closed connections,
       * there may be not be enough information to build a full response object.
       * The failure callback will be fired and this specific condition can be identified
       * by a status property value of 0.
       *
       * If an abort was successful, the status property will report a value of -1.
       *
       * @method createExceptionObject
       * @private
       * @static
       * @param {int} tId The Transaction Id
       * @param {callbackArg} callbackArg The user-defined argument or arguments to be passed to the callback
       * @param {boolean} isAbort Determines if the exception case is caused by a transaction abort
       * @return {object}
       */
        createExceptionObject:function(tId, callbackArg, isAbort)
        {
            var COMM_CODE = 0,
                COMM_ERROR = 'communication failure',
                ABORT_CODE = -1,
                ABORT_ERROR = 'transaction aborted',
                obj = {};

            obj.tId = tId;
            if(isAbort){
                obj.status = ABORT_CODE;
                obj.statusText = ABORT_ERROR;
            }
            else{
                obj.status = COMM_CODE;
                obj.statusText = COMM_ERROR;
            }

            if(callbackArg){
                obj.argument = callbackArg;
            }

            return obj;
        },

      /**
       * @description Method that initializes the custom HTTP headers for the each transaction.
       * @method initHeader
       * @public
       * @static
       * @param {string} label The HTTP header label
       * @param {string} value The HTTP header value
       * @param {string} isDefault Determines if the specific header is a default header
       * automatically sent with each transaction.
       * @return {void}
       */
        initHeader:function(label, value, isDefault)
        {
            var headerObj = (isDefault)?this._default_headers:this._http_headers;

            headerObj[label] = value;
            if(isDefault){
                this._has_default_headers = true;
            }
            else{
                this._has_http_headers = true;
            }
        },

      /**
       * @description Accessor that sets the HTTP headers for each transaction.
       * @method setHeader
       * @private
       * @static
       * @param {object} o The connection object for the transaction.
       * @return {void}
       */
        setHeader:function(o)
        {
            var prop;
            if(this._has_default_headers){
                for(prop in this._default_headers){
                    if(YAHOO.lang.hasOwnProperty(this._default_headers, prop)){
                        o.conn.setRequestHeader(prop, this._default_headers[prop]);
                        YAHOO.log('Default HTTP header ' + prop + ' set with value of ' + this._default_headers[prop], 'info', 'Connection');
                    }
                }
            }

            if(this._has_http_headers){
                for(prop in this._http_headers){
                    if(YAHOO.lang.hasOwnProperty(this._http_headers, prop)){
                        o.conn.setRequestHeader(prop, this._http_headers[prop]);
                        YAHOO.log('HTTP header ' + prop + ' set with value of ' + this._http_headers[prop], 'info', 'Connection');
                    }
                }

                this._http_headers = {};
                this._has_http_headers = false;
            }
        },

      /**
       * @description Resets the default HTTP headers object
       * @method resetDefaultHeaders
       * @public
       * @static
       * @return {void}
       */
        resetDefaultHeaders:function(){
            this._default_headers = {};
            this._has_default_headers = false;
        },

      /**
       * @description Method to terminate a transaction, if it has not reached readyState 4.
       * @method abort
       * @public
       * @static
       * @param {object} o The connection object returned by asyncRequest.
       * @param {object} callback  User-defined callback object.
       * @param {string} isTimeout boolean to indicate if abort resulted from a callback timeout.
       * @return {boolean}
       */
        abort:function(o, callback, isTimeout)
        {
            var abortStatus,
                args = (callback && callback.argument)?callback.argument:null;
                o = o || {};

            if(o.conn){
                if(o.xhr){
                    if(this.isCallInProgress(o)){
                        // Issue abort request
                        o.conn.abort();

                        window.clearInterval(this._poll[o.tId]);
                        delete this._poll[o.tId];

                        if(isTimeout){
                            window.clearTimeout(this._timeOut[o.tId]);
                            delete this._timeOut[o.tId];
                        }

                        abortStatus = true;
                    }
                }
                else if(o.xdr){
                    o.conn.abort(o.tId);
                    abortStatus = true;
                }
            }
            else if(o.upload){
                var frameId = 'yuiIO' + o.tId;
                var io = document.getElementById(frameId);

                if(io){
                    // Remove all listeners on the iframe prior to
                    // its destruction.
                    YAHOO.util.Event.removeListener(io, "load");
                    // Destroy the iframe facilitating the transaction.
                    document.body.removeChild(io);
                    YAHOO.log('File upload iframe destroyed. Id is:' + frameId, 'info', 'Connection');

                    if(isTimeout){
                        window.clearTimeout(this._timeOut[o.tId]);
                        delete this._timeOut[o.tId];
                    }

                    abortStatus = true;
                }
            }
            else{
                abortStatus = false;
            }

            if(abortStatus === true){
                // Fire global custom event -- abortEvent
                this.abortEvent.fire(o, args);

                if(o.abortEvent){
                    // Fire transaction custom event -- abortEvent
                    o.abortEvent.fire(o, args);
                }

                this.handleTransactionResponse(o, callback, true);
                YAHOO.log('Transaction ' + o.tId + ' aborted.', 'info', 'Connection');
            }

            return abortStatus;
        },

      /**
       * @description Determines if the transaction is still being processed.
       * @method isCallInProgress
       * @public
       * @static
       * @param {object} o The connection object returned by asyncRequest
       * @return {boolean}
       */
        isCallInProgress:function(o)
        {
            o = o || {};
            // if the XHR object assigned to the transaction has not been dereferenced,
            // then check its readyState status.  Otherwise, return false.
            if(o.xhr && o.conn){
                return o.conn.readyState !== 4 && o.conn.readyState !== 0;
            }
            else if(o.xdr && o.conn){
                return o.conn.isCallInProgress(o.tId);
            }
            else if(o.upload === true){
                return document.getElementById('yuiIO' + o.tId)?true:false;
            }
            else{
                return false;
            }
        },

      /**
       * @description Dereference the XHR instance and the connection object after the transaction is completed.
       * @method releaseObject
       * @private
       * @static
       * @param {object} o The connection object
       * @return {void}
       */
        releaseObject:function(o)
        {
            if(o && o.conn){
                //dereference the XHR instance.
                o.conn = null;

                YAHOO.log('Connection object for transaction ' + o.tId + ' destroyed.', 'info', 'Connection');

                //dereference the connection object.
                o = null;
            }
        }
    };

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