JSFiddle - React, Tailwind, and code Playground

HTML

<form enctype="multipart/form-data" action="/echo/html" method="post" name="fileinfo" accept-charset="windows-1251">
  <label>Label:</label>
  <input type="text" name="label" size="12" maxlength="32" value="привет får løbende" /><br />
  <input type="submit" value="Send standart">
</form>
<button onclick="sendForm()">Send ajax!</button>
<button onclick="sendFormEscaped()">Send escaped ajax!</button>
<button onclick="sendFormLikeBrowser()">Send ajax like the browser!</button>

JavaScript

window.sendForm = function() {
  var oOutput = document.getElementById("output"),
     oData = new FormData(document.forms.namedItem("fileinfo"));
  var oReq = new XMLHttpRequest();
  oReq.open("POST", "/echo/html", true);
  oReq.send(oData);
}
window.sendFormEscaped = function(){
    var oOutput = document.getElementById("output"),
     oData = new FormData();
    oData.append("label", escape(document.forms.namedItem("fileinfo").label.value));
  var oReq = new XMLHttpRequest();
  oReq.open("POST", "/echo/html", true);
  oReq.send(oData);
}
window.sendFormLikeBrowser = function(){
    var oOutput = document.getElementById("output"),
     oData = new FormData();
    oData.append("label", UnicodeToWin1251(document.forms.namedItem("fileinfo").label.value));
  var oReq = new XMLHttpRequest();
  oReq.open("POST", "/echo/html", true);
  oReq.send(oData);
}
function numericEscape(s){
    return s.replace(/[\u00A0-\u2666]/g, function(c) {
       return '&#'+c.charCodeAt(0)+';';
    });
}

// http://stackoverflow.com/a/2711936/1304559
var DMap = {0: 0, 1: 1, 2: 2, 3: 3, 4: 4, 5: 5, 6: 6, 7: 7, 8: 8, 9: 9, 10: 10, 11: 11, 12: 12, 13: 13, 14: 14, 15: 15, 16: 16, 17: 17, 18: 18, 19: 19, 20: 20, 21: 21, 22: 22, 23: 23, 24: 24, 25: 25, 26: 26, 27: 27, 28: 28, 29: 29, 30: 30, 31: 31, 32: 32, 33: 33, 34: 34, 35: 35, 36: 36, 37: 37, 38: 38, 39: 39, 40: 40, 41: 41, 42: 42, 43: 43, 44: 44, 45: 45, 46: 46, 47: 47, 48: 48, 49: 49, 50: 50, 51: 51, 52: 52, 53: 53, 54: 54, 55: 55, 56: 56, 57: 57, 58: 58, 59: 59, 60: 60, 61: 61, 62: 62, 63: 63, 64: 64, 65: 65, 66: 66, 67: 67, 68: 68, 69: 69, 70: 70, 71: 71, 72: 72, 73: 73, 74: 74, 75: 75, 76: 76, 77: 77, 78: 78, 79: 79, 80: 80, 81: 81, 82: 82, 83: 83, 84: 84, 85: 85, 86: 86, 87: 87, 88: 88, 89: 89, 90: 90, 91: 91, 92: 92, 93: 93, 94: 94, 95: 95, 96: 96, 97: 97, 98: 98, 99: 99, 100: 100, 101: 101, 102: 102, 103: 103, 104: 104, 105: 105, 106: 106, 107: 107, 108: 108, 109: 109, 110: 110, 111: 111, 112: 112, 113: 113, 114: 114, 115: 115,...