无法使用 java 脚本解析 xml DOM（来自文件）

Question

I've recently begun running into problems with javascript when I attempt to load element tags from a separate xml file into an html document. I know that I have enabled either XMLHttpRequest or activeX (depending on the internet browser) correctly, but I'm having problems getting the xml file and opening it to access it's tags. In order to open the file, I tried to use:

xhttp.open("GET",filepath,false);
xhttp.send();
xmlDoc=xhttp.responseXML;

the code appears to make it past the first line, but it gets tripped up at the second. I'm wondering if someone would be able to clarify the function of.send(), and if server permissions may by at fault; IE 7/8 it tells me "access is denied" when this block of code runs.

Answer 1

Make sure that ajax requests are sent to the same domain from the resources were accessed.

Taking your code sample here,

xhttp.open("GET",filepath,false);
xhttp.send();

You have requested for a resource with HTTP method GET. This request will be fired only once the send() method is called on the XHR object according to the specification[ 1 ]. The arguments for send() will be ignored if the method is GET.

Now once the xhr object is created, it goes through different states[ 2 ] such as

• UNSENT (numeric value 0)
• OPENED (numeric value 1)
• HEADERS_RECEIVED (numeric value 2)
• LOADING (numeric value 3)
• DONE (numeric value 4)

The moment the request is fired(ie, the send() is called), the xhr object will have a state of OPENED.

Now, if we look at the 3rd line of your code "xmlDoc=xhttp.responseXML;", it is quite unclear at what state you are trying to read the content. The best way to read the content is when the state reaches 4 or DONE

Just modify your code as given below:

 var xhr = new XMLHttpRequest();
    xhr.open("GET", somefilepath, true);
    xhr.send();
    xhr.onreadystatechange = function() {
     if(this.readyState == 4) {
      xmlDoc=xhr.responseXML;
     }
   }