Question

I got a requirement as following:

There is a link on a web page. As user clicks on link it should create a file on the fly and a download box pops up. How to do it using java script?

Answer 1

If the user trusts you, you can can create XML file directly in his filesystem.
Example code for Mozilla Firefox:

function mozillaSaveFile(filePath,content)
{
    if(window.Components) {
        try {
            netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
            var file = Components.classes["@mozilla.org/file/local;1"].createInstance(Components.interfaces.nsILocalFile);
            file.initWithPath(filePath);
            if(!file.exists())
                file.create(0,0664);
            var out = Components.classes["@mozilla.org/network/file-output-stream;1"].createInstance(Components.interfaces.nsIFileOutputStream);
            out.init(file,0x20|0x02,00004,null);
            out.write(content,content.length);
            out.flush();
            out.close();
            return true;
        } catch(ex) {
            return false;
        }
    }
    return null;
}

if you need support for all browsers, see how it is implemented in http://www.tiddlywiki.com

EDIT: This doesn’t work for Firefox 17+ because changing privileges was deemed unsafe and removed. see here for more details: https://bugzilla.mozilla.org/show_bug.cgi?id=546848#c57