document.getElementById（somevar）无法正常工作

Question

i have the code below but getElementById(setID) not working for me, i know it catches the id because alert(setID) working.

any idea?

function getdata(file, aID){
req = xmlHttpRequestHandler.createXmlHttpRequest();
req.onreadystatechange = Response;
req.open("GET", file, true);
req.send(null);
setID = aID;
}

function Response() { 
    var ready, status;
    try {
        ready = req.readyState;
        status = req.status;
    }
    catch(e) {}
    if (ready == 4 && status == 200) {
          document.getElementById("data").innerHTML = req.responseText;
    }

   document.getElementById(setID).className = "someclass";
}


<div class="msg" id="someid">
<a href="javascript:getdata('data.php', 'someid')">somelink</a>
</div>

Answer 1

Either use setID as a global variable or pass it to the callback function.

function getdata(file, aID)
{
    req = xmlHttpRequestHandler.createXmlHttpRequest();
    setID = aID;
    req.onreadystatechange = function() {Response(setID);};
    req.open("GET", file, true);
    req.send(null);
}

function Response(setID) 

Answer 2

If

document.getElementById("data")

doesn't work, this has one of the following reasons in 99% of all cases:

• The element does not exist or exist anymore

• There are more than one element with the id data

This happens often when the AJAX call introduces HTML code that also contains an element with the same ID.

Answer 3

Are you making your setID variable global? If not then try this:

var setID = null; // we set this here because it is referenced in functions

function getdata(file, aID){
req = xmlHttpRequestHandler.createXmlHttpRequest();
req.onreadystatechange = Response;
req.open("GET", file, true);
req.send(null);
setID = aID;
}

function Response() { 
    var ready, status;
    try {
        ready = req.readyState;
        status = req.status;
    }
    catch(e) {}
    if (ready == 4 && status == 200) {
          document.getElementById("data").innerHTML = req.responseText;
    }

   document.getElementById(setID).className = "someclass";
}