我使用 ajax 从 xml 获取数据。当我只使用一个 ajax 请求时它工作..当我添加第二个请求时，第一个请求停止工作..？为什么？有查询限制吗？
请求1（r1.php）
downloadUrl("gxml.php", function(data) {
var xml = data.responseXML;
var markers = xml.documentElement.getElementsByTagName("marker");
for (var i = 0; i < markers.length; i++) {
function bindInfoWindow(marker, map, infoWindow, html, category) {
google.maps.event.addListener(marker, 'click', function() {
infoWindow.setContent(html);
infoWindow.open(map, marker);
});
}
}
}
/********************** ***************************************/
function downloadUrl(url, callback) {
var request = window.ActiveXObject ?
new ActiveXObject('Microsoft.XMLHTTP') :
new XMLHttpRequest;
request.onreadystatechange = function() {
if (request.readyState == 4) {
request.onreadystatechange = doNothing;
callback(request, request.status);
}
};
request.open('GET', url, true);
request.send(null);
}
请求2（r2.php）
/**
* Returns an XMLHttp instance to use for asynchronous
* downloading. This method will never throw an exception, but will
* return NULL if the browser does not support XmlHttp for any reason.
* @return {XMLHttpRequest|Null}
*/
function createXmlHttpRequest() {
try {
if (typeof ActiveXObject != 'undefined') {
return new ActiveXObject('Microsoft.XMLHTTP');
} else if (window["XMLHttpRequest"]) {
return new XMLHttpRequest();
}
} catch (e) {
changeStatus(e);
}
return null;
};
/**
* This functions wraps XMLHttpRequest open/send function.
* It lets you specify a URL and will call the callback if
* it gets a status code of 200.
* @param {String} url The URL to retrieve
* @param {Function} callback The function to call once retrieved.
*/
function downloadUrl(url, callback) {
var status = -1;
var request = createXmlHttpRequest();
if (!request) {
return false;
}
request.onreadystatechange = function() {
if (request.readyState == 4) {
try {
status = request.status;
} catch (e) {
// Usually indicates request timed out in FF.
}
if ((status == 200) || (status == 0)) {
callback(request.responseText, request.status);
request.onreadystatechange = function() {};
}
}
}
request.open('GET', url, true);
try {
request.send(null);
} catch (e) {
changeStatus(e);
}
};
/**
* Parses the given XML string and returns the parsed document in a
* DOM data structure. This function will return an empty DOM node if
* XML parsing is not supported in this browser.
* @param {string} str XML string.
* @return {Element|Document} DOM.
*/
function xmlParse(str) {
if (typeof ActiveXObject != 'undefined' && typeof GetObject != 'undefined') {
var doc = new ActiveXObject('Microsoft.XMLDOM');
doc.loadXML(str);
return doc;
}
if (typeof DOMParser != 'undefined') {
return (new DOMParser()).parseFromString(str, 'text/xml');
}
return createElement('div', null);
}
/**
* Appends a JavaScript file to the page.
* @param {string} url
*/
function downloadScript(url) {
var script = document.createElement('script');
script.src = url;
document.body.appendChild(script);
}