File type validation with Javascript
<p>I have a question regarding to JavaScript validation. I am validaing the <code>&lt;input type="file"&gt;</code> whenever my scripts runs, it validates but also the action page is called. I want to stop the action page until the validation is complete. Here is my code, any help will be awesome. Regards</p>

<pre><code>&lt;!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"&gt;
&lt;html&gt;
    &lt;head&gt;
        &lt;meta http-equiv="Content-Type" content="text/html; charset=UTF-8"&gt;
        &lt;title&gt;Image Uploading&lt;/title&gt;
    &lt;/head&gt;


    &lt;body&gt;
        &lt;form name="xx" action="server.php" method="post" enctype="multipart/form-data" onsubmit="Checkfiles(this)"&gt;
            &lt;input type="file" name="file_uploading" id="filename"&gt;
            &lt;input type="submit" value="Submit" name="uploadfile"&gt;
        &lt;/form&gt;

        &lt;form name="view" method="post"&gt;
            &lt;a href="view_server.php"&gt;View your uploaded Images&lt;/a&gt;
        &lt;/form&gt;
    &lt;/body&gt;
&lt;/html&gt;

&lt;script type="text/javascript"&gt;
    function Checkfiles()
    {
        var fup = document.getElementById('filename');
        var fileName = fup.value;
        var ext = fileName.substring(fileName.lastIndexOf('.') + 1);

    if(ext =="GIF" || ext=="gif")
    {
        return true;
    }
    else
    {
        alert("Upload Gif Images only");
        return false;
    }
    }
&lt;/script&gt;
</code></pre>
