connection.js

这是YUI的源码及相关示例。里面有很多很炫的Javascript效果。

			// Determine if the argument is a form id or a form name.
			// Note form name usage is deprecated by supported
			// here for legacy reasons.
			oForm = (document.getElementById(formId) || document.forms[formId]);
		}
		else if(typeof formId == 'object'){
			// Treat argument as an HTML form object.
			oForm = formId;
		}
		else{
			return;
		}

		// If the isUpload argument is true, setForm will call createFrame to initialize
		// an iframe as the form target.
		//
		// The argument secureURI is also required by IE in SSL environments
		// where the secureURI string is a fully qualified HTTP path, used to set the source
		// of the iframe, to a stub resource in the same domain.
		if(isUpload){

			// Create iframe in preparation for file upload.
			this.createFrame(secureUri?secureUri:null);

			// Set form reference and file upload properties to true.
			this._isFormSubmit = true;
			this._isFileUpload = true;
			this._formNode = oForm;

			return;

		}

		// Iterate over the form elements collection to construct the
		// label-value pairs.
		for (i=0,len=oForm.elements.length; i<len; ++i){
			oElement  = oForm.elements[i];
			oDisabled = oElement.disabled;
            oName     = oElement.name;

			// Do not submit fields that are disabled or
			// do not have a name attribute value.
			if(!oDisabled && oName)
			{
                oName  = encodeURIComponent(oName)+'=';
                oValue = encodeURIComponent(oElement.value);

				switch(oElement.type)
				{
                    // Safari, Opera, FF all default opt.value from .text if
                    // value attribute not specified in markup
					case 'select-one':
                        if (oElement.selectedIndex > -1) {
                            opt = oElement.options[oElement.selectedIndex];
                            data[item++] = oName + encodeURIComponent(
                                (opt.attributes.value && opt.attributes.value.specified) ? opt.value : opt.text);
                        }
                        break;
					case 'select-multiple':
                        if (oElement.selectedIndex > -1) {
                            for(j=oElement.selectedIndex, jlen=oElement.options.length; j<jlen; ++j){
                                opt = oElement.options[j];
                                if (opt.selected) {
                                    data[item++] = oName + encodeURIComponent(
                                        (opt.attributes.value && opt.attributes.value.specified) ? opt.value : opt.text);
                                }
                            }
                        }
						break;
					case 'radio':
					case 'checkbox':
						if(oElement.checked){
                            data[item++] = oName + oValue;
						}
						break;
					case 'file':
						// stub case as XMLHttpRequest will only send the file path as a string.
					case undefined:
						// stub case for fieldset element which returns undefined.
					case 'reset':
						// stub case for input type reset button.
					case 'button':
						// stub case for input type button elements.
						break;
					case 'submit':
						if(hasSubmit === false){
							if(this._hasSubmitListener && this._submitElementValue){
                                data[item++] = this._submitElementValue;
							}
							else{
                                data[item++] = oName + oValue;
							}

							hasSubmit = true;
						}
						break;
					default:
                        data[item++] = oName + oValue;
				}
			}
		}

		this._isFormSubmit = true;
		this._sFormData = data.join('&');


		this.initHeader('Content-Type', this._default_form_header);

		return this._sFormData;
	},

  /**
   * @description Resets HTML form properties when an HTML form or HTML form
   * with file upload transaction is sent.
   * @method resetFormState
   * @private
   * @static
   * @return {void}
   */
	resetFormState:function(){
		this._isFormSubmit = false;
		this._isFileUpload = false;
		this._formNode = null;
		this._sFormData = "";
	},

  /**
   * @description Creates an iframe to be used for form file uploads.  It is remove from the
   * document upon completion of the upload transaction.
   * @method createFrame
   * @private
   * @static
   * @param {string} optional qualified path of iframe resource for SSL in IE.
   * @return {void}
   */
	createFrame:function(secureUri){

		// IE does not allow the setting of id and name attributes as object
		// properties via createElement().  A different iframe creation
		// pattern is required for IE.
		var frameId = 'yuiIO' + this._transaction_id;
		var io;
		if(YAHOO.env.ua.ie){
			io = document.createElement('<iframe id="' + frameId + '" name="' + frameId + '" />');

			// IE will throw a security exception in an SSL environment if the
			// iframe source is undefined.
			if(typeof secureUri == 'boolean'){
				io.src = 'javascript:false';
			}
		}
		else{
			io = document.createElement('iframe');
			io.id = frameId;
			io.name = frameId;
		}

		io.style.position = 'absolute';
		io.style.top = '-1000px';
		io.style.left = '-1000px';

		document.body.appendChild(io);
	},

  /**
   * @description Parses the POST data and creates hidden form elements
   * for each key-value, and appends them to the HTML form object.
   * @method appendPostData
   * @private
   * @static
   * @param {string} postData The HTTP POST data
   * @return {array} formElements Collection of hidden fields.
   */
	appendPostData:function(postData)
	{
		var formElements = [],
			postMessage = postData.split('&'),
			i, delimitPos;
		for(i=0; i < postMessage.length; i++){
			delimitPos = postMessage[i].indexOf('=');
			if(delimitPos != -1){
				formElements[i] = document.createElement('input');
				formElements[i].type = 'hidden';
				formElements[i].name = decodeURIComponent(postMessage[i].substring(0,delimitPos));
				formElements[i].value = decodeURIComponent(postMessage[i].substring(delimitPos+1));
				this._formNode.appendChild(formElements[i]);
			}
		}

		return formElements;
	},

  /**
   * @description Uploads HTML form, inclusive of files/attachments, using the
   * iframe created in createFrame to facilitate the transaction.
   * @method uploadFile
   * @private
   * @static
   * @param {int} id The transaction id.
   * @param {object} callback User-defined callback object.
   * @param {string} uri Fully qualified path of resource.
   * @param {string} postData POST data to be submitted in addition to HTML form.
   * @return {void}
   */
	uploadFile:function(o, callback, uri, postData){

		// Each iframe has an id prefix of "yuiIO" followed
		// by the unique transaction id.
		var frameId = 'yuiIO' + o.tId,
		    uploadEncoding = 'multipart/form-data',
		    io = document.getElementById(frameId),
		    oConn = this,
			args = (callback && callback.argument)?callback.argument:null,
            oElements,i,prop,obj;

		// Track original HTML form attribute values.
		var rawFormAttributes =
		{
			action:this._formNode.getAttribute('action'),
			method:this._formNode.getAttribute('method'),
			target:this._formNode.getAttribute('target')
		};

		// Initialize the HTML form properties in case they are
		// not defined in the HTML form.
		this._formNode.setAttribute('action', uri);
		this._formNode.setAttribute('method', 'POST');
		this._formNode.setAttribute('target', frameId);

		if(YAHOO.env.ua.ie){
			// IE does not respect property enctype for HTML forms.
			// Instead it uses the property - "encoding".
			this._formNode.setAttribute('encoding', uploadEncoding);
		}
		else{
			this._formNode.setAttribute('enctype', uploadEncoding);
		}

		if(postData){
			oElements = this.appendPostData(postData);
		}

		// Start file upload.
		this._formNode.submit();

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

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

		// Start polling if a callback is present and the timeout
		// property has been defined.
		if(callback && callback.timeout){
			this._timeOut[o.tId] = window.setTimeout(function(){ oConn.abort(o, callback, true); }, callback.timeout);
		}

		// Remove HTML elements created by appendPostData
		if(oElements && oElements.length > 0){
			for(i=0; i < oElements.length; i++){
				this._formNode.removeChild(oElements[i]);
			}
		}

		// Restore HTML form attributes to their original
		// values prior to file upload.
		for(prop in rawFormAttributes){
			if(YAHOO.lang.hasOwnProperty(rawFormAttributes, prop)){
				if(rawFormAttributes[prop]){
					this._formNode.setAttribute(prop, rawFormAttributes[prop]);
				}
				else{
					this._formNode.removeAttribute(prop);
				}
			}
		}

		// Reset HTML form state properties.
		this.resetFormState();

		// Create the upload callback handler that fires when the iframe
		// receives the load event.  Subsequently, the event handler is detached
		// and the iframe removed from the document.
		var uploadCallback = function()
		{
			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);
			}

			obj = {
			    tId : o.tId,
			    argument : callback.argument
            };

			try
			{
				// responseText and responseXML will be populated with the same data from the iframe.
				// Since the HTTP headers cannot be read from the iframe
				obj.responseText = io.contentWindow.document.body?io.contentWindow.document.body.innerHTML:io.contentWindow.document.documentElement.textContent;
				obj.responseXML = io.contentWindow.document.XMLDocument?io.contentWindow.document.XMLDocument:io.contentWindow.document;
			}
			catch(e){}

			if(callback && callback.upload){
				if(!callback.scope){
					callback.upload(obj);
				}
				else{
					callback.upload.apply(callback.scope, [obj]);
				}
			}

			// Fire global custom event -- uploadEvent
			oConn.uploadEvent.fire(obj);

			if(o.uploadEvent){
				// Fire transaction custom event -- uploadEvent
				o.uploadEvent.fire(obj);
			}

			YAHOO.util.Event.removeListener(io, "load", uploadCallback);

			setTimeout(
				function(){
					document.body.removeChild(io);
					oConn.releaseObject(o);
				}, 100);
		};

		// Bind the onload handler to the iframe to detect the file upload response.
		YAHOO.util.Event.addListener(io, "load", uploadCallback);
	},

  /**
   * @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;
		var args = (callback && callback.argument)?callback.argument:null;


		if(o && o.conn){
			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 && o.isUpload === true){
			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);

				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);
		}

		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)
	{
		// if the XHR object assigned to the transaction has not been dereferenced,
		// then check its readyState status.  Otherwise, return false.
		if(o && o.conn){
			return o.conn.readyState !== 4 && o.conn.readyState !== 0;
		}
		else if(o && o.isUpload === true){
			var frameId = 'yuiIO' + o.tId;
			return document.getElementById(frameId)?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;


			//dereference the connection object.
			o = null;
		}
	}
};
YAHOO.register("connection", YAHOO.util.Connect, {version: "2.6.0", build: "1321"});