preview image before a download with javascript code example

Example 1: preview image file upload javascript

<input type="file" accept="image/*" onchange="loadFile(event)">
<img id="output"/>
<script>
  var loadFile = function(event) {
    var output = document.getElementById('output');
    output.src = URL.createObjectURL(event.target.files[0]);
    output.onload = function() {
      URL.revokeObjectURL(output.src) // free memory
    }
  };
</script>

Example 2: 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);
});