Ajax-For循环

Ajax calls an array of four strings, I then want to print each string to a new line. I have this code:

window.onload = function () {
    var obj;
    var xmlhttp;

    if (window.XMLHttpRequest) {
        xmlhttp = new XMLHttpRequest();
    } else {
        xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }

    xmlhttp.onreadystatechange = function () {
        if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
            obj = JSON.parse(xmlhttp.responseText);

            for (var i = 0; i <= obj.length; i++) {
                document.createTextNode(obj[i]);
            }
        }
    }

    xmlhttp.open("GET", "verify.php", true);
    xmlhttp.send();
}

However, it doesn't work. obj.length returns 4, I don't know whether the loop isn't executing, or if I can't access the DOM? I'm very new to Javascript and DOM scripting.

Thanks in advance.

This only creates the textNode, you must still apply it to the DOM somehwere via appendChild:

https://developer.mozilla.org/en/DOM/document.createTextNode

You need to actually put the nodes into the document.

var node;
for (var i = 0, n = obj.length; i < n; i++) {  // NB: not <=
    node = document.createTextNode(obj[i]);
    document.body.appendChild(node);

    node = document.createElement('br');
    document.body.appendChild(node);
}