title: Random characters always return zero
body: <p>In this snippet it will generate mixed words and numbers randomly but i'm wondering why it always return zero in second character? if you click refresh button it always return 0 in second position. any idea?</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>$(function() {
    var words = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZ0123456789abcdefghiklmnopqrstuvwxyz"
    var myLength = 4;
  
    function Captcha() {
      $('#Captcha').html("");
      for (var i = 0; i &lt; myLength; i++) {
        var word = words[Math.floor(Math.random() * words.length)];
        $('#Captcha').append(word + i++);
      }
    }
      Captcha();
   $('#reCaptchaRefresh').click(function(){
    Captcha();
    });
  });</code></pre>
  <pre class="snippet-code-css lang-css prettyprint-override"><code>#Captcha {
  border: 1px solid black;
    padding: 10px;
    float: left;
  }
  
  #reCaptchaRefresh {
  clear: both;  
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"&gt;&lt;/script&gt;
  &lt;div id="Captcha" &gt;&lt;/div&gt;
  &lt;div id="reCaptchaRefresh"&gt;
  Refresh
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>