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function doRequest(method,url,async,onLoad,onProgress) {
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var xhr;
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if ((onProgress || isXDomainUrl(url)) && window.XDomainRequest) {
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// if it is x-domain or streaming/incremental updates are needed we will use IE's XDomainRequest for IE
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// streaming/interactive mode is broken in IE's XHR, but for some reason works in XDR (with onprogress), so we will
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// need to use XDR if incremental updates are necessary
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// see bug https://connect.microsoft.com/IE/feedback/ViewFeedback.aspx?FeedbackID=334813
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if (url.match(/^https:/) && !onProgress) {
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// XDR doesn’t work for secure https communication
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// see bug https://connect.microsoft.com/IE/feedback/ViewFeedback.aspx?FeedbackID=333380
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loadUsingScriptTag(url); // script tag insertion can be more secure than XDR
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// in some situations because it supports https
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return;
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}
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xhr = new XDomainRequest;
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// relative paths don’t work in XDomainRequest, see bug https://connect.microsoft.com/IE/feedback/ViewFeedback.aspx?FeedbackID=333275
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if (!url.match(/^http:/)) { // test to see if it is an absolute url
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url = absoluteUrl(location.href,url); // must have a function to turn it into an absolute url
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}
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if (!(method == “GET” || method == “POST”)) {
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// XDomainRequest does not support methods besides GET and POST
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// see bug https://connect.microsoft.com/IE/feedback/ViewFeedback.aspx?FeedbackID=334809
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// We will try to add the method as a parameter and hope the server will understand… good luck :/
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url += “&method=” + method;
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method = “POST”;
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}
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function xdrLoad() {
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if (xhr.contentType.match(/\/xml/)){
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// there is no responseXML in XDomainRequest, so we have to create it manually
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var dom = new ActiveXObject(”Microsoft.XMLDOM”);
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dom.async = false;
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dom.loadXML(xhr.responseText,200);
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onLoad(dom);
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}
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else {
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onLoad(xhr.responseText,200); // we will assume that the status code is 200, XDomainRequest rejects all other successful status codes
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// see bug https://connect.microsoft.com/IE/feedback/ViewFeedback.aspx?FeedbackID=334804
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}
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}
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if (async === false) {
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// XDomainRequest does not support synchronous requests
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// see bug https://connect.microsoft.com/IE/feedback/ViewFeedback.aspx?FeedbackID=336031
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// so we will try to block execution on our own (which is not really possible in any reasonable manner)
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var loaded;
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xhr.onload = function() {
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loaded = true;
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xdrLoad();
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}
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xhr.open(method,url);
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xhr.send(null);
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while(!loaded) { // try to block until the response is received
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// I am sure the user won’t mind just clicking OK so we can block execution
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alert(”Waiting for the response, please click OK because it probably is here now”);
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}
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return;
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}
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else { // do an asynchronous request with XDomainRequest
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xhr.onload = xdrLoad;
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xhr.open(method,url);
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xhr.onprogress = onProgress;
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}
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}
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// we will mercifully skip all the branches for ActiveXObject(”Microsoft.XMLHTTP”) to accomodate IE6 and lower
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else {
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xhr = new XMLHttpRequest; // use the standard XHR for same origin and browsers that implement cross-site
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// W3C requests and streaming
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xhr.open(method,url,async);
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xhr.onreadystatechange = function() {
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if (xhr.readyState == 3) // interactive mode
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onProgress(xhr.responseText);
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if (xhr.readyState == 4) // finished
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onLoad(xhr.responseText,xhr.status);
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}
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}
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xhr.send(null); // finally send the request whether it be XDR or XHR
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// and supporting functions
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function absoluteUrl : function(baseUrl, relativeUrl) {
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// This takes a base url and a relative url and resolves the target url.
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// For example:
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// resolveUrl(”http://www.domain.com/path1/path2″,”../path3″) ->”http://www.domain.com/path1/path3″
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//
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if (relativeUrl.match(/\w+:\/\//))
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return relativeUrl;
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if (relativeUrl.charAt(0)==’/') {
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baseUrl = baseUrl.match(/.*\/\/[^\/]+/)
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return (baseUrl ? baseUrl[0] : ”) + relativeUrl;
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}
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//TODO: handle protocol relative urls: ://www.domain.com
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baseUrl = baseUrl.substring(0,baseUrl.length - baseUrl.match(/[^\/]*$/)[0].length);// clean off the trailing path
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if (relativeUrl == ‘.’)
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return baseUrl;
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while (relativeUrl.substring(0,3) == ‘../’) {
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baseUrl = baseUrl.substring(0,baseUrl.length - baseUrl.match(/[^\/]*\/$/)[0].length);
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relativeUrl = relativeUrl.substring(3);
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}
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return baseUrl + relativeUrl;
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}
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function loadUsingScriptTag(url) {
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… do JSONP here if we want
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}
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}
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