Xml Dom解析返回null

Question

I am new to html and javascript. 我是html和javascript的新手。 I have been trying to parse and access the data of an xml file through the javascript code. 我一直在尝试通过javascript代码解析和访问xml文件的数据。 Presently it is showing null. 目前它显示为空。 I am posting my codes below. 我在下面发布我的代码。 Please have a look and do help. 请看看并提供帮助。

    Html code:

        <!DOCTYPE html>
    <html>
    <meta http-equiv="content-type" content="text/html; charset=utf-8" />
    <body>

    <p id="demo"></p>

    <script>
    var xhttp;
    xhttp = new XMLHttpRequest();
    xhttp.onreadystatechange = function() {
        if (this.readyState == 4 && this.status == 200) {
            myFunction(this);
        }
    };
    xhttp.open("GET", "http://10.21.64.222/LoadBreakSwitch/LBS_Commands.xml", true);
    xhttp.send();

    function myFunction(xml) {
        var x, i, txt, xmlDoc; 
        xmlDoc = xml.responseXML;
        txt = "";
        x = xmlDoc.getElementsByTagName("Ping");
        for (i = 0; i < x.length; i++) { 
            txt += x[i].childNodes[0].nodeValue + "<br>";
        }
        document.getElementById("demo").innerHTML = txt;
    }
    </script>
    </body>
    </html>

The xml file:

    <?xml version="1.0" encoding="utf-8"?>

<LBSCommands>
  <Ping Commkey="A3070000AA00A4" Value="A309008001043101A4"/>
  <Frequency Commkey="A3070300AD00A4" CommValue="A309038001013101A4"/>
  <SwitchStatus Commkey="A3071D01C800A4" CommValue="A3091D8101014C01A4"/>

</LBSCommands>

Answer 1

I'm not sure what exactly you mean by "it is showing null", but maybe changing your code to using onload callback would help: 我不确定“显示为空”的确切含义，但也许将代码更改为使用onload回调会有所帮助：

var xhttp;
xhttp = new XMLHttpRequest();
xhttp.onload = function() {
    myFunction(this);
};

Also, this line: txt += x[i].childNodes[0].nodeValue + "<br>"; 另外，这一行： txt += x[i].childNodes[0].nodeValue + "<br>"; will throw an exception since childNodes[0] is undefined in your XML document. 由于XML文档中undefined childNodes[0]因此将引发异常。

EDIT: 编辑：

To make x[i].childNodes[0] non-null, you must move the desired attribute to be the child element's text value. 要使x[i].childNodes[0]不为空，必须将所需的属性移动为子元素的文本值。 For instance, if you replace: 例如，如果您替换：

<Ping Commkey="A3070000AA00A4" Value="A309008001043101A4"/>

with: 有：

<Ping>
    <Commkey key="A3070000AA00A4">
        A309008001043101A4
    <Commkey/>
<Ping/>

(and do the same to the rest of the elements) then you'll have something like: （并对其余元素执行相同操作），那么您将得到类似以下内容的信息：

 <p id="demo">
      A309008001043101A4<br>
      A309038001013101A4<br>
      A3091D8101014C01A4<br>
 </p>

as your HTML. 作为您的HTML。

If that's not the exact HTML outcome you want please show an example HTML so I'll be able to help. 如果这不是您想要的确切HTML结果，请显示HTML示例，以便我提供帮助。

Xml Dom解析返回null

问题描述

1 个解决方案

解决方案1
0 2016-11-25 07:56:41

Xml Dom解析返回null

问题描述

1 个解决方案

解决方案1 0 2016-11-25 07:56:41

解决方案1
0 2016-11-25 07:56:41