JAVASCRIPT

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>

upload preview image js

// <input type="file" accept="image/*" id="img-input">
// <img id="preview"/>
function readURL(input) {
      if (input.files && input.files[0]) {
          var reader = new FileReader();
          reader.onload = function(e) {
          $('#preview').attr('src', e.target.result);
          }
          reader.readAsDataURL(input.files[0]);
      } else {
          $('#preview').attr('src', '');
      }
    }

  $("#img-input").change(function() {
    readURL(this);
  });

Javascript Image Preview Before Upload

imgInp.onchange = evt => {
  const [file] = imgInp.files
  if (file) {
    blah.src = URL.createObjectURL(file)
  }
}