Reverse text button for Google Translate

gt-reverse.js

// ==UserScript==
// @name     Google U.G.E.
// @version  1.1
// @grant    none
// @include  https://translate.google.com/*
// ==/UserScript==

window.addEventListener('load', function() {
    var btn = document.createElement('div');
  btn.setAttribute('class', 'jfk-button-standard jfk-button-narrow jfk-button');
  btn.setAttribute('role', 'button');
  btn.setAttribute('data-tooltip', 'Reverse characters');
  btn.style.float = 'right';
  btn.innerText = 'cbA';
  
  var source = document.getElementById('source');
  btn.addEventListener('click', function() {
    var newStr = '';
    for (var i=source.value.length-1; i>=0; --i) {
      newStr += source.value[i];
    }
    source.value = newStr;
  });
  
  var gtswap = document.getElementById('gt-swap');
  gtswap.parentNode.appendChild(btn);
});