Jaitnium Jaitnium - 3 months ago 16
Ajax Question

How do I check if a folder exists over https

I'm hosting a webpage on github (flickrTest.html) and I'm trying to check the existence of a folder in the same directory as the webpage. The hosted folder looks like this:
http://imgur.com/a/pZWoH

I try to use an ajax call like this:

$.ajax({
url: 'mapData',
error: function() {
//Ddirectory doesn't exist
console.log("ERROR: expected directory named 'mapData'. Exiting...");
return
},
success: function() {
//Directory does exist
console.log("mapData exists..");
...


but I'm getting a mixed-content error because this call is considered http and the site my webpage is being hosted on is https. Somehow I'm able to access mapData's JSON files if I include the absolute path. Is there a way to check for the existence of a folder over https?

Answer

First, there is a fundamental problem with your approach. As others have stated in comments, you cannot check if a folder has contents (or exists) with a simple http (or https) web request since the web server will expect to respond with HTML that can be presented as information for a user's browser. You can create a handler or script that will process a directory request and map that functionality using something like a .htaccess rule or other rewrite system depending on what platform you are on. The reason why I've identified this as a "problem" and have not gone as far to say it's impossible, is because you can (as it appears you are attempting) parse that response into something usable. That said, I think it's beside the point and not the nature of the error you are actually getting.

The error you are experiencing is coming from loading the current page you are on in HTTPS and the ajax request you are making is over HTTP (as indicated by the error message). This message can be misleading in your case since it's not that the request URL has not been identified as HTTPS, it's because the browser doesn't trust that the URL is a Web request to either a file or a folder. You can correct this by simply adding a trailing slash to the folder:

$.ajax({
        url: 'mapData/',
        error: function() {
            //Ddirectory doesn't exist
            console.log("ERROR: expected directory named 'mapData'. Exiting...");
            return
        },
        success: function() {
            //Directory does exist
            console.log("mapData exists..");
         ...

You have now resolved the issue of completing the web request, but you are faced with a problem that is mentioned in the first part. The server will return a 404 error because that is how github.io is configured to respond to empty (or non-existent) directory requests. You will need some type of server-side handler to process this request, or you will need to come up with something else creative such as putting an index.html in that folder so that your JavaScript can parse the result. For instance, you could drop an index.html in the folder and if the server returns 200, then you know the folder exists, but if it returns 404 then you can assume the folder does not exist.

In case it's not already known, web servers are designed to make it so that a browser is limited in reverse-engineering it's content. While servers can be configured to return directory contents, by default, most are going to protect folders so that remote users cannot browse the server without some type of elevated permissions/authentication. Essentially, the reason why this requires a a more customized server-side approach is not because there is something wrong with the front-end code, it's because the web server is designed to not allow this type of thing without the server being configured to allow it due to security.

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