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141 lines
3.7 KiB
141 lines
3.7 KiB
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/**
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* @class Ajax
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*
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* Perform asynchronous call to the server.
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*
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* documentation:
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* http://ajaxpatterns.org/HTTP_Streaming
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* http://ajaxpatterns.org/XMLHttpRequest_Call
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* http://www.skill-guru.com/blog/2011/02/04/adding-access-control-allow-origin-to-server-for-cross-domain-scripting/
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*
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* @author Jos de Jong, Almende, 2011
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*/
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var Ajax = function() {
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this.isBusy = true;
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this.timer = undefined;
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this.req = undefined;
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this.callback = undefined;
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// for long poll
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this.pollCallback = undefined;
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this.pollInterval = 1000; // milliseconds
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this.lastResponseLength = 0;
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}
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/**
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* Make a request
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* @param {string} method The call method: typically "GET" or "POST"
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* @param {string} url The url to be called, for example "mydata.php"
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* @param {method} callback The callback method, which will be called when
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* the response is received. The response is passed
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* as a plain text (string) parameter to this method:
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* callback(response);
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*/
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Ajax.prototype.request = function(method, url, callback)
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{
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var me = this;
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this.isBusy = true;
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this.callback = callback;
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this.req = (XMLHttpRequest)? new XMLHttpRequest(): new ActiveXObject("MSXML2.XMLHTTP");
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this.req.onreadystatechange = function() { me._checkReadyState(); };
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this.req.open(method, url, true);
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this.req.send(null);
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}
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/**
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* Make a long poll request.
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* This poll can be stopped via Ajax.abort();
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* @param {string} method The call method: typically "GET" or "POST"
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* @param {string} url The url to be called, for example "mydata.php"
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* @param {method} callback The callback method, which will be called
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* repeatedly, each time that new data is received.
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* The newly received data is passed
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* as a plain text (string) parameter to this method:
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* callback(response);
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*/
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Ajax.prototype.requestLongPoll = function(method, url, callback)
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{
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this.request(method, url);
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var me = this;
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this.pollCallback = callback;
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this.lastResponseLength = 0;
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this.timer = setInterval(function() {me._checkResponse();}, this.pollInterval);
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}
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/**
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* Cancel a current request
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*/
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Ajax.prototype.abort = function() {
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this.isBusy = false;
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if (this.timer) {
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clearInterval(this.timer)
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this.timer = undefined;
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}
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if (this.req) {
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this.req.abort();
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this.req = undefined;
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}
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}
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/**
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* The callback method which is called when a response is received.
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*/
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Ajax.prototype._checkReadyState = function()
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{
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switch(this.req.readyState)
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{
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case 1: break;
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case 2: break;
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case 3: break;
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case 4:
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if (this.callback) {
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this.callback(this.req.responseText);
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}
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// reset all variables
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this.abort();
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}
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}
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/**
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* Callback function executed repeatedly during a long poll.
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* The currently received response data is checked, and all new data is passed
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* to the callback function.
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*/
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Ajax.prototype._checkResponse = function() {
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var len = this.req.responseText.length;
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if (len > this.lastResponseLength) {
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var newData = this.req.responseText.substring(this.lastResponseLength);
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// TODO: clear the current responseText here, to prevent the response
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// from growing infinitely?
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if (this.pollCallback) {
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this.pollCallback(newData);
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}
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this.lastResponseLength = len;
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}
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}
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/**
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* Set the interval for long polling
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* @param {number} interval Interval in milliseconds
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*/
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Ajax.prototype.setPollInterval = function(interval) {
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this.pollInterval = interval;
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}
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/**
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* get the poll interval
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*/
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Ajax.prototype.getPollInterval = function() {
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return this.pollInterval;
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}
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