JSFiddle - React, Tailwind, and code Playground

JavaScript

// ==UserScript==
// @name        ftp photo preview
// @namespace   ftp://*/*
// @version     1
// @grant       none
// @require  http://ajax.googleapis.com/ajax/libs/jquery/1.3/jquery.min.js
// ==/UserScript==
var preview_ext = ['jpg', 'jpeg', 'png', 'bmp'];
$('.file').hover(function(){
	var file = $(this),
			filename = file.attr('href'),
			extension = filename.substring(filename.lastIndexOf(".")+1, filename.length).toLowerCase();

	if( preview_ext.some(function(ext){return ext==extension;}) ){
		file.text('').append($('<img style="width:200px; height:auto; max-width:100%; max-height:100%;" src="'+filename+'">'));
	}
});