Node.js + Express: Upload a file without reloading page

I am creating a chat application using Node.js, and would like to have a file upload feature. While I can get the file uploaded, the browser would always be redirected to another link or page refreshed, and this of course disrupts the chat.

First I tried using Express to do it:

index.html:

<form id="fileSendButton" action="/" method="post" enctype="multipart/form-data">
    <input type="text" name="title"><br>
    <input type="file" name="upload" multiple="multiple"><br>
    <input type="submit" value="Upload">
</form> 

app.js:

app.post('/', function(req, res){
    //some validation and rename file
    res.send();
    return false;
});

Next I tried using AJAX, but still couldnt do it, whenever the AJAX POST to the Node.js server, it would reload the page. My AJAX code anyway:

index.html:

$.ajax({  
    type: "POST",  
    url: "/",  
    data: formdata,  
    processData: false,
    contentType: false,
    success: function (res) {
        document.getElementById("chatText").innerHTML = res; 
    } 
});  
return false;

Third I went to look at Uploadify, but didnt want to add Flash dependancy to my site, so I didnt implement it.

Anyone can help me please? I dont want a page reload when a file is uploaded.