JSFiddle - React, Tailwind, and code Playground

HTML

<div id="info"></div>

JavaScript

var s = 'fdlfdskkjhflkdsjlkjfdaiauoeinafpodndpoifnspdofposaiptoaipojpodfmpoampofmdpofampodsajfpgojdsapogmapomgpoamgpoamgpodmagpoajoigudsalijsltnmaigvshvin;LVNV;LINFPNDS;LKNFIDSANGLASDNGFLDSNLNSlknfldnlgnlgnfdglisndlgndslifg';

function test1(s) {
  var x = 0;
  for (var i = 0; i < 100000; i++) {
    for (var p = 0; p < s.length; p++) {
      if (s[p] === 'l') x++;
    }
  }
  return x;
}

function test2(s) {
  var x = 0;
  for (var i = 0; i < 100000; i++) {
    for (var p = 0; p < s.length; p++) {
      if (s.charAt(p) === 'l') x++;
    }
  }
  return x;
}

function log() {
  var s = [];
  for (var i = 0; i < arguments.length; i++) {
    s.push(arguments[i] ? JSON.stringify(arguments[i]) : arguments[i]);
  }
  document.getElementById('info').innerHTML += '<br/>' + s.join(', ');
}

function time(name, func) {
  var start = +new Date();
  func();
  var end = +new Date();
  log(name + ':' + (end - start));
}

time('indexer', function() {
  console.log(test1(s));
});
time('charAt', function() {
  console.log(test2(s));
});
String.prototype.test1 = function() {
  test1(this);
}
String.prototype.test2 = function() {
  test2(this);
}
time('indexer boxed', function() {
  console.log(s.test1());
});
time('charAt boxed', function() {
  console.log(s.test2());
});