How to check duplicate of my input file upload?
<p>I have this form which has a button for file upload.  When you select a file it shows at upload_prev div. 
My problem is that when I try to select the same file nothing happens.  I would like a validation or kind of non duplication function to run.
I did that. I tried many things and methods like using child nodes and seeing if the inner text is the same.  I tried to loop using jquery each and getting the value, but all of them failed.  I want to display a message that this file is already in the Box of upload_prev when I select it again.</p>

<pre><code>&lt;!DOCTYPE html&gt;
&lt;html&gt;
&lt;head&gt;
  &lt;meta http-equiv="content-type" content="text/html; charset=UTF-8"&gt;

  &lt;script type="text/javascript" src="https://code.jquery.com/jquery-1.10.1.js"&gt;&lt;/script&gt;

      &lt;link rel="stylesheet" type="text/css" href="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/css/bootstrap-combined.min.css"&gt;

      &lt;link rel="stylesheet" type="text/css" href="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/css/bootstrap-combined.min.css"&gt;

  &lt;style type="text/css"&gt;
    .fileUpload {
  position: relative;
  overflow: hidden;
  margin: 10px;
}

.fileUpload input.upload {
  position: absolute;
  top: 0;
  right: 0;
  margin: 0;
  padding: 0;
  font-size: 20px;
  cursor: pointer;
  opacity: 0;
  background-color: #fff;
  filter: alpha(opacity=0);
}

.buttonwrap {
  text-align: center;
  padding-top: 20px;
  float: left;
  display: block;
}

.buttonsend:hover {
  background-color: rgba(255, 255, 255, 0.2);
  color: #225C51;
}

.buttonsend {
  text-decoration: none;
  color: #fff;
  font-size: 18px;
  padding-top: 5px;
  padding-bottom: 5px;
  padding-left: 10px;
  padding-right: 10px;
  background-color: rgba(72, 133, 130, .5);
}

span {
  float: left;
  display: flex;
  width: 100%;
}

p.closed {
  margin: 0 0 0 7px;
  cursor: pointer;
}

  &lt;/style&gt;

  &lt;title&gt;&lt;/title&gt;

&lt;script type='text/javascript'&gt;//&lt;![CDATA[

$(window).load(function(){  
//  TO CLOSE THE SLECTED FILE
$(document).on('click', '.close', function() {
  $(this).parents('span').remove();
})

//JUST TO PUT A VALUE IN THE BOX WHICH HAS 
document.getElementById("uploadBtn").onchange = function() {
  document.getElementById("uploadFile").value = this.value;
};

document.getElementById('uploadBtn').onchange = uploadOnChange;
//document.getElementById('uploadBtn').onchange = myFunction;


function uploadOnChange() {

  var filename = this.value;
  var lastIndex = filename.lastIndexOf("\\");
  if (lastIndex &gt;= 0) {
    filename = filename.substring(lastIndex + 1);
  }


//  alert (filename);

  var files = $('#uploadBtn')[0].files;

  for (var i = 0; i &lt; files.length; i++) {
    $("#upload_prev").append('&lt;span&gt;' + '&lt;div class="hesh"&gt;' + files[i].name +'&lt;/div&gt;' + '&lt;p class="close"&gt;X&lt;/p&gt;&lt;/span&gt;');
  }
  document.getElementById('filename').value = filename;

        document.getElementById("demo").innerHTML = files.length;

}


});//]]&gt; 

&lt;/script&gt;


&lt;/head&gt;

&lt;body&gt;
  &lt;FORM METHOD="post" ACTION="" ENCTYPE="multipart/form-data"&gt;
&lt;!--  &lt;input id="uploadFile" placeholder="Add files from My Computer" class="steptextboxq3" /&gt;--&gt;
  &lt;div class="fileUpload btn btn-primary"&gt;
    &lt;span&gt;Browse&lt;/span&gt;
    &lt;input id="uploadBtn" type="file" class="upload" multiple="multiple" name="browsefile" /&gt;
  &lt;/div&gt;
  &lt;input id="filename" type="text" /&gt;

  &lt;div id="upload_prev"&gt;&lt;/div&gt;


  &lt;div style="clear:both;"&gt;&lt;/div&gt;
  &lt;div class="buttonwrap"&gt;
    &lt;a href="contactus.html" class="buttonsend" style="float:right;"&gt;Send &lt;/a&gt; &lt;/div&gt;
&lt;/FORM&gt;

    &lt;p id="demo"&gt;&lt;/p&gt;

&lt;/body&gt;

&lt;/html&gt;
</code></pre>

<p>This is my fiddle. How can I find a way to do this.</p>

<p><a href="https://jsfiddle.net/Lc5gb7c9/" rel="nofollow">https://jsfiddle.net/Lc5gb7c9/</a></p>