Recursive call affecting parent method variables?

I am building nested comments. My AJAX script gets a list of comments like follows and expands them -

    if (xmlhttp.readyState == 4 || myOb.readyState == "complete")   {
        // EVAL
        var comments = eval('(' + xmlhttp.responseText + ')');

        // POPULATE
        var comm = "<ul>";
        for(i = 0; i < comments.length; i++)    {               
            if(comments[i].replyto == 0)    {
                comm = comm + expand(property, comments, i);
            }
        }
        comm = comm + "</ul>";
        // DISPLAY
        document.getElementById("comments").innerHTML =开发者_如何学C comm;
    }

Here, the expand function is recursive, and seems to be causing trouble -

function expand(property, comments, k)  {
    var comm = "";

    // PRINT MAIN COMMENTS
    comm = comm + "<li>";
        // print otherparent comment data

        // replies
        comm = comm + "<ul>";
        for(i = 0; i < comments.length; i++)    {
            // is a reply?
            if(comments[i].replyto == comments[k].id)   {
                comm = comm + expand(property, comments, i);
            }
        }
        comm = comm + "</ul>";

    comm = comm + "</li>";
    return comm;
}

This script ends up giving my only the first comments array element (with it's respective sub-comments). But if i remove the recursive bit of code, I don't face that problem (also, i don t get any sub-comments)..

function expand(property, comments, k)  {
    var comm = "";

    // PRINT MAIN COMMENTS
    comm = comm + "<li>";
        // print otherparent comment data

        // replies
        comm = comm + "<ul>";
        /*
        for(i = 0; i < comments.length; i++)    {
            // is a reply?
            if(comments[i].replyto == comments[k].id)   {
                comm = comm + expand(property, comments, i);
            }
        }
        */
        comm = comm + "</ul>";

    comm = comm + "</li>";
    return comm;
}

I set two alerts in the eval function, one each before and after the expand call:

        for(i = 0; i < comments.length; i++)    {               
            if(comments[i].replyto == 0)    {
                alert(i);
                comm = comm + expand(property, comments, i);
                alert(i);
            }
        }

Both gave me different values of i. What am i doing wrong?

Thanks

You forgot to make "i" a local variable:

    for(var i = 0; i < comments.length; i++)    {               

That's really important.