how to preview uploaded image in html code example

Example 1: how to display image before upload in jhtml

function display(input) {
   if (input.files && input.files[0]) {
      var reader = new FileReader();
      reader.onload = function(event) {
         $('#myid').attr('src', event.target.result);
      }
      reader.readAsDataURL(input.files[0]);
   }
}

$("#demo").change(function() {
   display(this);
});

Example 2: file upload preview in html

<html>
<head>
<script type='text/javascript'>
function preview_image(event) 
{
 var reader = new FileReader();
 reader.onload = function()
 {
  var output = document.getElementById('output_image');
  output.src = reader.result;
 }
 reader.readAsDataURL(event.target.files[0]);
}
</script>
<style>
body
{
 width:100%;
 margin:0 auto;
 padding:0px;
 font-family:helvetica;
 background-color:#0B3861;
}
#wrapper
{
 text-align:center;
 margin:0 auto;
 padding:0px;
 width:995px;
}
#output_image
{
 max-width:300px;
}
</style>
</head>
<body>
<div id="wrapper">
 <input type="file" accept="image/*" onchange="preview_image(event)">
 <img id="output_image"/>
</div>
</body>
</html>