JSFiddle - React, Tailwind, and code Playground

HTML

<dl> <dt><label for="fileupload">{L_FILENAME}:</label></dt>

    <dd>
        <input type="file" name="fileupload" id="fileupload" maxlength="{FILESIZE}" value="" />
    </dd>
</dl>

JavaScript

$(document).ready(function () {
    $("#fileupload").change(function (e) {
        var val = $(this).val();
        if (val.match(/(?:gif|jpg|JPG|JPEG|png|PNG|bmp)$/)) {
            alert("You are trying to upload an image. Please use the image uploader!");
        }
    });
});