代码不起作用(未捕获的引用错误：未定义$ajaxUtils))

document.addEventListener("DOMContentLoaded", function (event) {
showLoading("#main-content");
$ajaxUtils.sendGetRequest(
homeHtml,
function (responseText) {
document.querySelector("#main-content").innerHTML = responseText;
},
false);
});

因此，制作一个新的ajax-utils.js文件，并在其中使用以下代码：

(function(global) {
// Set up a namespace for our utility
var ajaxUtils = {};

// Returns an HTTP request object
function getRequestObject() {
if (window.XMLHttpRequest) {
return (new XMLHttpRequest());
} 
else if (window.ActiveXObject) {
// For very old IE browsers (optional)
return (new ActiveXObject("Microsoft.XMLHTTP"));
} 
else {
global.alert("Ajax is not supported!");
return(null); 
}
}

// Makes an Ajax GET request to 'requestUrl'
ajaxUtils.sendGetRequest = 
function(requestUrl, responseHandler, isJsonResponse) {
var request = getRequestObject();
request.onreadystatechange = 
function() { 
handleResponse(request, 
responseHandler,
isJsonResponse); 
};
request.open("GET", requestUrl, true);
request.send(null); // for POST only
};

// Only calls user provided 'responseHandler'
// function if response is ready
// and not an error
function handleResponse(request,
responseHandler,
isJsonResponse) {
if ((request.readyState == 4) &&
(request.status == 200)) {
// Default to isJsonResponse = true
if (isJsonResponse == undefined) {
isJsonResponse = true;
}
if (isJsonResponse) {
responseHandler(JSON.parse(request.responseText));
}
else {
responseHandler(request.responseText);
}
}
}

// Expose utility to the global object
global.$ajaxUtils = ajaxUtils;

})(window);

确保将ajax-query.js链接到index.html页面：(