Is there any way, by using JavaScript, to check if a certain file exists in a full URL's directory? I have an image of a green light and an image of a red light. If the file exists in the directory I would like the green light to be shown, if not, then I would like the red light to be shown. Is this possible and can anyone help me out with this? All I need is the most simple form of the code determining whether it is found or not, then displaying either image. I think I would be able to take it from there.

Thanks in advance to anyone who can help me.

I would use a server-side programming language (e.g. ASP) to do this. People can disable/not use Javascript. They can't do that with ASP/PHP.

Its just something I'm making as a personal project. It will be mostly used from my computer's local directories, so I'm keeping the whole page HTML and JavaScript only.

No then it won't be possible.
For security reasons JavaScript doesn't have any functions for file handling.

Regards,
Insensus

I'm pretty sure it's possible though. I found this bit of coding, but I don't understand how to make it work.

if("cover.jpg" exist)
document.write('<img src='cover.jpg'>')
else
//display nothing

That's no code.
It's an example of someone who doesn't know about JavaScript and hopes that this piece of fake coding illustrates good enough what he wants for someone to tell him how to do so.
It still isn't possible.

Regards,
Insensus

But what about this one: http://irt.org/script/52.htm

Is there any way I can use something similar to that, and check a file instead of an image?

That's still not polling the file system. It's just attaching an error handler to the image tag. Not at all the same thing.

The other snippet is what's called "pseudo-code." Assuming it's what you're trying to do, though, why not just use the img tag, and accept the red X if the file doesn't exist?

Javascript is called "client-side programming" for a reason... it can't manipulate the server files or client files... would you really want a javascript program deleting your hard drive while you were crusing the net?

Originally Posted by JGiannotti

Its just something I'm making as a personal project. It will be mostly used from my computer's local directories, so I'm keeping the whole page HTML and JavaScript only.

Since this is the case, then yes you absolutely can.
On windows systems you can create what is called an HTA (HyperText Application) which is escentially an HTML file (with an HTA extension) where your javascript has full system access, files, registry, network, etc... You just access those items through built in ActiveX controls. The MSDN site can give you all you need, just google the term.

On Linux, w/ KDE, you can also do something very similar as well as remote control other applications through the DCOP sytem.

I'm not sure how you'd do it on a Mac. But, since their claim to fame is usability, I'm sure there is something.

Maybe I was being a bit vague.

I plan on using the file on my computer, to check up on various sites on the internet which I don't have access to. I just need the JavaScript to check up on a URL and simply give me a yes or no if it can access it.

you can use the HttpRequest Object to retrieve the HTTP Response for the document.

Its not possible for a file without resorting to an Ajax call or some other mechanism to hit the server. But, just for information sake if the file is an image then you can check by using the onError attribute on an image tag. For example;

<img src="http://www.somehost.com/myimage.jpg" onerror="alert('Image missing')">

See http://www.irt.org/script/52.htm for more

I know the original post was a while ago, but as this is still high up when you google this topic, thought I would post to help others.

Yes, checking links is possible if you have the following:

1. Custom error pages: Directions to create custom error pages can be found at http://en.wikipedia.org/wiki/Custom_error_page and http://www.outfront.net/tutorials_02...tomerrors1.htm

2. Opera browser, would be more productive that Internet Explorer or Firefox because IE asks for confirmation every time a page tries to close itself.

What to do: In custom error page, add the below code to close the window automatically.

<script>
window.close()
</script>

Now paste the below code in a blank text file and save it as .html file.
Now open that html file in your browser and start checking links.

<html>

<head>
<script>
function check()
{
webAdd=prompt("Enter url here in given format: www.google.com","www.google.com")
{
window.open("http://"+webAdd+"")
}
}
</script>
</head>

<body>
<input type="button" value="Check URL" onclick="check()">
</body>

</html>

If you are going to use it on localhost, you can customize the webAdd that way so that you will need to enter only the file name at prompt box.

Rationale behind this trick:
If file exists > Fill will load
If file does not exist > Custom error page loads > Custom error page closes due to inserted javascript code > User returns to the window in which he was previously there(i.e,-URL checking page)

So If you return to the file checking page, it means file does not exist.