Getting random value with javascript

Guys i am trying to get random values when click a button and made that code but when i click somehow one value repeat itself 4 times like "k0k2k4k6" , "n0n2n4n6". Why this happenning?Cos its not a coincidence. Thanks in advance! JSFIDDLE

$(function() {
  var words = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz"
  var word = words[Math.floor(Math.random() * words.length)];
  var myLength = 8;

  function random() {
    for (var i = 0; i < myLength; i++) {
      $('#content').append(word + i++);
    }
  }

  $('#button').click(function() {
    random();
  });

});

#content {
  width: 200px;
  height: 50px;
  border: 1px solid #333;
  margin-top: 50px;

<script src="http://ift.tt/1oMJErh"></script>
<button id="button">Click</button>
<div id="content"></div>