API: connection connection_core.js (YUI Library)

# Yahoo! UI Library

### connection 2.8.1

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 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 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;
    			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 o,t,args = (callback && callback.argument)?callback.argument:null;

    		if(this._isFileUpload){
    			t = 'upload';
    		}
    		else if(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){
    					this.uploadFile(o, callback, uri, postData);
    					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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