How to Verify if an Image Exists on the Server with JavaScript?

Verifying Image Availability on the Server with JavaScript

In web development scenarios, it might be necessary to determine if a specific image file exists on the server before using it in the user interface. JavaScript provides a method to check for image existence, enabling dynamic and real-time updates to web pages.

To achieve this, one can utilize the XMLHttpRequest object, which allows for the sending and receiving of data from a server using JavaScript. The following code snippet illustrates how to check if an image exists:

function imageExists(image_url) {
    var http = new XMLHttpRequest();
    http.open('HEAD', image_url, false);
    http.send();
    return http.status != 404;
}

This function performs an HTTP HEAD request to the specified image URL. The HEAD request retrieves only the header information of the resource, without downloading the entire image. If the HTTP status code returned is not 404 (Not Found), it indicates that the image exists on the server.

Alternatively, using jQuery can simplify the process:

$.get(image_url)
    .done(function() {
        // Do something now you know the image exists.
    })
    .fail(function() {
        // Image doesn't exist - do something else.
    })

In this example, jQuery's $.get() function sends an HTTP GET request to the image URL. If the request succeeds (HTTP status code is not 404), the done() callback function is executed; otherwise, the fail() callback function is invoked.

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