How do I detect if a browser can open Network Folder inside iframe?

Question

I need to alert users browsing with Chrome that they need to open a page using IE, as it allow open a Network Folder inside iframe.

But I don't want to detect browser, is there a way to detect this feature?

Answer 1

No, you cannot detect this feature (if you can call it that, allowing web pages to display local folders in a frame is a very bad idea). The same-origin policy prevents you from knowing what was loaded into the frame so you cannot distinguish a network folder from an error page. Best you can do is checking how long the frame takes to load:

var start = new Date().getTime();
var frame = document.createElement("iframe");
frame.addEventListener("load", function()
{
  if (new Date().getTime() - start < 100)
    alert("Looks like the network folder didn't load, try using a less secure browser?");
}, false);
frame.src = "file://mynetworkpath/folder";
document.body.appendChild(frame);

In my tests it took Chrome around 30 milliseconds to load the error page, the code above sets 100 milliseconds as threshold just to be sure. Loading a network folder should always take considerably longer. This code didn't work in Firefox 30, for some reason the load event isn't fired there. This might be a security precaution but I don't really know that.

Alternatively, you can try loading an image that is known to exist:

var img = new Image();
img.onload = function()
{
  // Can display the frame
};
img.onerror = function()
{
    alert("Try using a less secure browser?");
};
img.src = "file://mynetworkpath/folder/pixel.gif";

Note that neither solution will allow distinguishing between "browser won't let me access network folders" and "network folder is inaccessible, probably no network connection."