IF File Exists Javascript

Question

Can anyone see anything wrong with this? It stops the image changing when the image is not here as I want but it does not change the image all the time when it does!

Cheers, Shaun

var myFile = "/_images/multi/" + productCode + "/" + imgCodeAlt + "_l.jpg";
if (myFile.exists()) {
    $("#imgMain img").attr({
        rel: 'lightbox',
        src: "/_images/multi/" + productCode + "/" + imgCodeAlt + "_l.jpg"
    });
}

`@`Shaun: You read wrong. You're calling `exists()` on a ***string***, not a file. — Matt, Jul 23 '12 at 10:59
possible duplicate of [How do I check if file exists in jQuery or Javascript?](http://stackoverflow.com/questions/3646914/how-do-i-check-if-file-exists-in-jquery-or-javascript) — Felix Kling, Jul 23 '12 at 11:11

score 1 · Answer 1 · answered Jul 23 '12 at 10:57

1

You can't check for files existing in Javascript due to it being a client side language.

You could try an ajax request to the file, and if it returns a 404 status code, the file does not exist - seems messy though.

answered Jul 23 '12 at 10:57

royse41

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JavaScript is not a client-side language. It's true that the OP is *using* it client-side in this case, though. – T.J. Crowder Jul 23 '12 at 10:58
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You can also create a `new Image()`, set the `src`, and listen for the `onerror` event. – Matt Jul 23 '12 at 10:58
@T.J.Crowder spot on - but having seeing his initial code i tried to keep my answer simple... – royse41 Jul 23 '12 at 10:59
@Dennis i tried to provide a very rough solution to maybe help them them on their way... – royse41 Jul 23 '12 at 11:02

score 1 · Answer 2 · edited May 23 '17 at 11:56

1

I dont think there is a exists function in javascript which can check if a file exists on some location. If you really want to check existence of file the only way you can do it in js is using ajax. check this post How do I check if file exists in jQuery or JavaScript?

edited May 23 '17 at 11:56

Community

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answered Jul 23 '12 at 10:58

sushil bharwani

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score 1 · Accepted Answer · answered Jul 23 '12 at 11:08

1

Your code will work if you define exists like this:

String.prototype.exists = function() {
    var a = new XMLHttpRequest;
    a.open( "GET", this+"", false );
    a.send( null );
    return a.status === 200;
};

"/".exists() //true

answered Jul 23 '12 at 11:08

Esailija

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score 0 · Answer 4 · answered Jul 23 '12 at 10:58

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What is exists() for? If you're trying to check if the file exists from JavaScript, then this isn't going to work using that method in JS.

I would suggest using an AJAX call if you need to verify the existence of a file.

answered Jul 23 '12 at 10:58

Rhys

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IF File Exists Javascript

4 Answers4