JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.2.4/jquery.min.js"></script>
<input type="file" name="pic" accept="image/*">

<div>
  <div class="string">Converted string : <span class="result"></span></div>
  <div class="filename">Converted filename : <span class="result"></span></div>
</div>

JavaScript

$(document).on('change', 'input[type=file]', function() {

    var files = this.files;

    for (var i = 0; i < files.length; i++) {
      (function(file) {
        // Assuming the file name is áñǽŦõş
        var _string = 'áñǽŦõş.jpg',
            _filename = file.name;

        $('.string .result').html(convertAscii(_string));
        $('.filename .result').html(convertAscii(_filename));

      })(files[i]);
    }
    
});
    
function convertAscii(str) {

	  str = str.replace(/Ä/g, 'Ae');
    str = str.replace(/æ|ǽ|ä/g, 'ae');
    str = str.replace(/À|Á|Â|Ã|Å|Ǻ|Ā|Ă|Ą|Ǎ|А/g, 'A');
    str = str.replace(/à|á|â|ã|å|ǻ|ā|ă|ą|ǎ|ª|а/g, 'a');
    str = str.replace(/Б/g, 'B');
    str = str.replace(/б/g, 'b');
    str = str.replace(/Ç|Ć|Ĉ|Ċ|Č|Ц/g, 'C');
    str = str.replace(/ç|ć|ĉ|ċ|č|ц/g, 'c');
    str = str.replace(/Ð|Ď|Đ/g, 'Dj');
    str = str.replace(/ð|ď|đ/g, 'dj');
    str = str.replace(/Д/g, 'D');
    str = str.replace(/д/g, 'd');
    str = str.replace(/È|É|Ê|Ë|Ē|Ĕ|Ė|Ę|Ě|Е|Ё|Э/g, 'E');
    str = str.replace(/è|é|ê|ë|ē|ĕ|ė|ę|ě|е|ё|э/g, 'e');
    str = str.replace(/Ф/g, 'F');
    str = str.replace(/ƒ|ф/g, 'f');
    str = str.replace(/Ĝ|Ğ|Ġ|Ģ|Г/g, 'G');
    str = str.replace(/ĝ|ğ|ġ|ģ|г/g, 'g');
    str = str.replace(/Ĥ|Ħ|Х/g, 'H');
    str = str.replace(/ĥ|ħ|х/g, 'h');
    str = str.replace(/Ì|Í|Î|Ï|Ĩ|Ī|Ĭ|Ǐ|Į|İ|И/g, 'I');
    str = str.replace(/ì|í|î|ï|ĩ|ī|ĭ|ǐ|į|ı|и/g, 'i');
    str = str.replace(/Ĵ|Й/g, 'J');
    str = str.replace(/ĵ|й/g, 'j');
    str = str.replace(/Ķ|К/g, 'K');
    str = str.replace(/ķ|к/g, 'k');
    str = str.replace(/Ĺ|Ļ|Ľ|Ŀ|Ł|Л/g, 'L');
    str = str.replace(/ĺ|ļ|ľ|ŀ|ł|л/g, 'l');
    str = str.replace(/М/g, 'M');
    str = str.replace(/м/g, 'm');
    str = str.replace(/Ñ|Ń|Ņ|Ň|Н/g, 'N');
    str = str.replace(/ñ|ń|ņ|ň|ʼn|н/g, 'n');
    str = str.replace(/Ö/g, 'Oe');
    str = str.replace(/œ|ö/g, 'oe');
    str = str.replace(/Ò|Ó|Ô|Õ|Ō|Ŏ|Ǒ|Ő|Ơ|Ø|Ǿ|О/g, 'O');
    str = str.replace(/ò|ó|ô|õ|ō|ŏ|ǒ|ő|ơ|ø|ǿ|º|о/g, 'o');
    str =...