Use jQuery To Retrieve Data From An XML File

Question

function readXMLData(tagName){
    var result;
    function loadfail(){
        alert("Error");
    }

    function parse(document){
        $(document).find(tagName).each(function(){
            result = $(this).find('value').text();
        });
    }

    $.ajax({
        type: "GET",
        url: 'config.xml',
        dataType: 'xml',
        success: parse,
        error: loadfail
    });

    //alert(result);
    return result;
}

<?xml version="1.0" encoding="UTF-8" ?>
<config>
    <host-prefix>
        <value>myprefix</value>
    </host-prefix>

    <host-url>
        <value>localhost</value>
    </host-url>

    <image-path>
        <value>imagePath</value>
    </image-path>
</config>

i have this xml file, and i need to retrieve data from it to use these data in another jquery function i call this function by readXMLData("host-prefix") .

if i call function as i mentioned above, it returns undefined , whoever if i uncomment the alert(result) in readXMLData function, alert appears with undefined text but function return myprefix (the true result). 如果我如上所述调用函数，则返回undefined ，如果我在readXMLData函数中取消对alert(result)的readXMLData ，则出现带有undefined文本的警报，但是函数返回myprefix （真实结果）。 and everything works fine. i need to remove alert(result) from my code i function still works proparly.

any help?

Answer 1

call the readXMLData() function as following. Since ajax is asynchronous, it will not get you the result at once, so, that's why it alerts 'undefined'.

var result;
var requiredTagName;

function readXMLData(tagName)
{
         requiredTagName  = tagName;

         $.ajax({
            type: "GET",
            url: 'config.xml',
            dataType: 'xml',
            success: parse,
            error: loadfail
        });
}
   function loadfail()
   {
       alert("Error");
   }

   function parse(document)
   {
        $(document).find(requiredTagName).each(function(){
             result = $(this).find('value').text();
        });
   }

Answer 2

You shouldnt attempt to return data from a ajax function. Ajax is by definition asynchronus, so you never know when the result will come back, and execution will not halt until there is a return. Thus you should plan to call a callback... for example:

function readXMLData(tagName, callback){
    var result;

    if(typeof callback != 'function) {
       return false;
    }

    function loadfail(){
        alert("Error");
    }

    function parse(document){
        $(document).find(tagName).each(function(){
            result = $(this).find('value').text();
            callback(result);
        });
    }

    $.ajax({
        type: "GET",
        url: 'config.xml',
        dataType: 'xml',
        success: parse,
        error: loadfail
    });

    // we return true or false which indicates that we fired off the request ok
    // and nothing more.
    return true;
}

So then what you would do is you would call it by passing in the the next function you need to call that takes the result and does something with it:

readXMLData("host-prefix", yourNextFunction);