Untitled

<html>
<head>
<title>base64test</title>
</head>
<form>
  <input id="file" type="file" />
</form>

<input id="button" type="button" value="encode"/>
<br />
<textarea id="encoded" style="width:1000px; height:800px;"></textarea>

<script type="text/javascript">
  document.getElementById('button').onclick=function(){
    console.log("button clicked.");
    var form =  document.querySelector("#file").files[0];
    getBase64(form);
  }

  function getBase64(file) {
     var reader = new FileReader();
     reader.readAsDataURL(file);
     reader.onload = function () {
       document.querySelector('#encoded').value = reader.result;
     };
     reader.onerror = function (error) {
       console.log('Error: ', error);
     };
  }
</script>
</html>